The KelvinTrack Android app
Far more than a thermometer. The app reads your KelvinTag sensors over Bluetooth, turns an Android phone left on site into a relay to the internet, and its AI engine analyses the thermal signature of your equipment to warn you when a component starts to weaken - before it fails.
- 3 years of readings in the sensor
- No missing points
- Bluetooth up to 50 m
- No location permission
The essentials
A classic thermometer answers "is it cold enough right now?". The KelvinTrack app answers a far more useful question: "is my equipment degrading?". Free on Google Play (Android 12+), it reads your KelvinTag sensors over Bluetooth up to 50 m, turns a phone left on site into a relay with no subscription, and its AI watches the health of every refrigeration part. Each sensor holds 3 years of readings in memory: even away from the phone, no point is ever lost.
Updated September 2026.
How the relay works
The sensor measures and records on its own. For readings and alerts to leave the site, you need a relay: an Android phone left on site, which reads the sensors over Bluetooth and sends everything over the internet. It is the only hardware besides the sensors, and it carries no subscription.
Setting up the relay
- An Android 12 or newer phone, with the free KelvinTrack app from Google Play.
- Placed on site, within Bluetooth range of the sensors: up to 50 m depending on the environment.
- Plugged in: that is our recommendation, so it stays on day and night.
- Connected to the internet, over WiFi or with a SIM card (mobile data).
- Battery set to "Unrestricted": the app guides you through it during setup on Samsung, Xiaomi and OnePlus.
- After that it runs by itself: the app works in the background with a permanent notification and restarts on its own after a phone reboot, an app update or being swiped away. Only a force-stop halts it, until it is opened again.
Allow 15 to 30 minutes, no technician needed. One phone follows at least 7 KelvinTag sensors. Alerts reach the phones of the people concerned, iPhones included: the app guide (iPhone and Android) explains how. An iPhone receives alerts but cannot act as the relay.
What if...
- I take the phone home
- The sensors are out of range: they keep recording to their memory, and the readings catch up automatically when the phone comes back. But while it is away, no live alert can go out.
- The phone loses internet
- The readings stay on the phone and upload when the connection returns. No alert leaves the site while it is offline: the alerts arrive once the connection is back.
- The phone switches off or breaks down
- The sensors keep recording. On the dashboard they show a warning after 1 hour without news, then go offline after 4 hours. No email, SMS or push is sent about the relay itself: hence a dedicated, plugged-in phone.
- I use my personal phone
- It is technically possible, but as soon as it leaves the site the sensors are out of range and no live alert goes out. We recommend a dedicated Android phone, left on site.
Predictive diagnostics of cold-chain components
Every part of a refrigeration system - compressor, refrigerant, condenser, defrost, fan - leaves a signature in the temperature curve. An outright failure is almost always preceded by weeks of small signals. The human eye misses them; KelvinTrack's AI, trained to recognise these signatures in the continuous readings, does not. It turns those signals into a clear, component-by-component status.
Here, five parts are healthy, the thermostat has been flagged "to check" for three days, and the fan is not measurable in this setup. The message is concrete: a technical intervention is recommended in the coming weeks - not an emergency on a Sunday night.
In all honesty: temperature monitoring reveals symptoms, it does not replace a technician diagnosis - it orients it and triggers it at the right time. Some signatures confirm over time and sharpen with several sensors. Not every failure is announced: a sudden mechanical break can still happen.
Four early signals, readable in the curve
Most failures begin with a slow drift, not a sudden stop. The value shift is going from reactive to preventive: acting during the alert window, while a maintenance visit is still enough.
| Early signal | What it often reveals |
|---|---|
| The baseline rises by a few tenths over several days | Refrigerant leak, fouling, tired compressor |
| Recovery time lengthens after each opening or defrost | Loss of capacity (refrigerant, condenser, fan) |
| Cycles get closer together or become erratic | Door seal, controller, compressor short-cycling |
| The defrost pattern changes | Failing defrost heater or timer |
The full reasoning, part by part, is detailed in our approach to compliance and prevention.
No measurement point ever lost
The KelvinTag sensor is not a mere transmitter: it is a standalone logger holding 3 years of readings in its own memory. Relay off, phone away, internet down: it keeps recording, point by point.
When you come back in range, the app detects the gap in the history and quickly pulls the missing points over Bluetooth. Your curve is complete, with no manual step - and that curve is what stands as proof during an inspection.
Bluetooth range reaches up to 50 m depending on the environment: walls and cold-room panels shorten it, so place the relay phone as close to the sensors as you can.
Spec sheet
- Sensor memory
- 3 years of readings, no missing points
- Catch-up
- Fast retrieval of missing points when back in range
- Bluetooth range
- Up to 50 m depending on the environment
- Minimum Android
- Android 12
- Location
- No location permission requested
- Price
- Free on Google Play, no subscription
Privacy included: the app scans Bluetooth without ever asking for your location.
What the app does
Bluetooth relay, up to 50 m
Reads your KelvinTag sensors over Bluetooth up to 50 m depending on the environment. An Android 12 or newer phone, left on site, becomes the relay over WiFi or mobile data - with no recurring cost.
AI predictive diagnostics
The AI analyses each unit's thermal signature and flags the component that is weakening before an outright failure.
3-year memory, zero gaps
Each KelvinTag holds 3 years of readings in its memory. Back in range, the app quickly pulls the missing points: the curve stays complete.
Real-time alerts
Threshold breaches trigger an immediate alert, relayed to your dashboard and your notifications.
HACCP history
The full history is kept and stands as proof during an inspection - continuous traceability, at night, on weekends and holidays.
Free, no subscription
Free on Google Play, no per-sensor subscription. Install it on as many phones as you need; each device in range strengthens coverage.
Frequently asked questions about the Android app
How does the app detect a weakening component?
- Every part of a refrigeration system leaves a signature in the temperature curve. By tracking that curve continuously, the app spots the slow drifts that precede a failure - a rising baseline, a lengthening recovery time, a changing defrost pattern - and flags the component to check.
Does the diagnosis replace a refrigeration technician?
- No. Temperature monitoring reveals symptoms; it does not replace a technician diagnosis, it orients it and triggers it at the right time. Some signatures confirm over time and sharpen with several sensors. Not every failure is announced: a sudden mechanical break can still happen.
Do I need a dedicated gateway to use this app?
- No. The relay is an Android 12 or newer phone running this free app, left on site within Bluetooth range of the sensors (up to 50 m depending on the environment); we recommend keeping it plugged in. It sends the readings over WiFi or mobile data to the dashboard, which alerts the people concerned by email, SMS and push notification, iPhones included. No gateway to buy, no subscription.
Does the relay phone have to stay on site? Can I use my personal phone?
- It is technically possible with a personal phone, but as soon as it leaves the site the sensors are out of range: they keep recording to their memory and the readings catch up when it returns, but no live alert can go out while it is away. We therefore recommend a dedicated Android phone, left on site and plugged in.
What happens if the relay phone loses its internet connection?
- The readings are kept on the phone and upload automatically as soon as the connection returns. However, no alert leaves the site while it is offline: the alerts arrive once the connection is back. The phone can use WiFi or the mobile data of a SIM card.
Am I warned if the relay phone stops working?
- Not by email, SMS or push: no message is sent about the relay itself. The dashboard shows a warning when a sensor has not reported for 1 hour, then shows it as offline after 4 hours. The sensors keep recording in the meantime. That is why we recommend a dedicated phone, left on site and plugged in: the app runs in the background and restarts itself after a phone reboot or an app update.
How many sensors can a single relay phone follow?
- At least 7 sensors per phone, guaranteed, as long as they are within Bluetooth range (up to 50 m depending on the environment).
What happens if I move away from the sensors? Are readings lost?
- None. Each KelvinTag sensor is a standalone logger holding 3 years of readings in its own memory, relay present or not. As soon as the phone comes back into Bluetooth range (up to 50 m depending on the environment), the app detects the missing points and quickly pulls them in: the curve stays complete, with no manual step. The one limit: while the phone is out of range, no live alert can go out.
Which Android version is required?
- Android 12 or newer. This choice also lets the app scan Bluetooth without requesting the location permission: it never knows your position.
Where can I download the Android app?
- The app is available for free on Google Play. Install it on an Android 12 or newer phone, leave it on site within range of the sensors, connected over WiFi or mobile data, and readings flow automatically to your dashboard.
Listen to what your cold chain is telling you
Download the free Android app: installed on an Android 12 or newer phone left on site, it turns it into a relay with no subscription.