Tempdrop is a wearable sensor worn on the upper arm during sleep that measures basal body temperature continuously — eliminating the need to wake at the same time every morning for a manual thermometer reading. It syncs overnight temperature data to the Tempdrop app and third-party platforms including Apple Health and Kindara. We tested it for six weeks alongside Oura Ring 4.
Tempdrop is a single-purpose wearable: a small sensor worn on the upper arm overnight that measures skin temperature continuously during sleep. Where a traditional basal body temperature thermometer requires measurement at a fixed time each morning before getting out of bed, Tempdrop samples temperature throughout the night and applies an algorithm to derive a comparable resting temperature reading — meaning irregular wake times, night shifts, and disrupted sleep schedules don't invalidate the measurement.
It is a temperature measurement device. It measures one thing: overnight body temperature. What users do with that data — which app they feed it into, which patterns they track — is entirely separate from the hardware.
| Spec | Tempdrop Gen 2 |
|---|---|
| Sensor placement | Upper arm (worn in armband) |
| Measurement method | Continuous overnight skin temperature |
| Battery life | ~6 months (replaceable coin cell) |
| Water resistance | IPX7 |
| Connectivity | Bluetooth (syncs to phone app in morning) |
| Integrations | Tempdrop app, Apple Health, Kindara, Read Your Body, others |
| Price | $129 one-time |
| Subscription | None required for hardware use |
The hardware is small and unobtrusive — the sensor pod is approximately the size of a large coin, worn in a soft fabric armband. The battery lasts approximately six months and is a standard replaceable coin cell (CR2032), so there's no charging routine and no wired connection. Build quality is solid. The armband is washable.
Tempdrop samples skin temperature on the upper arm at regular intervals throughout the night. The device's proprietary algorithm analyses the full overnight temperature curve — accounting for movement, position changes, and ambient temperature variation — to derive a stable resting temperature reading. This is the key differentiator from a standard oral thermometer: the algorithm compensates for factors that would otherwise produce noise in the reading.
In the morning, opening the Tempdrop app syncs the overnight data via Bluetooth. The app displays the derived temperature reading, a confidence score for that reading, and the raw overnight temperature curve. From there, data can be exported to Apple Health or third-party cycle tracking apps.
We wore Tempdrop and Oura Ring 4 simultaneously for six weeks to compare overnight temperature data. Both devices detected the characteristic overnight temperature pattern — the gradual drop in the first part of the night and the pre-wake rise. The Oura Ring's finger placement provides a more stable signal with less ambient temperature noise than the upper arm; on nights with significant movement or variable room temperature, Oura's readings were more consistent. However, Tempdrop's algorithm compensation narrowed this gap considerably on most nights.
For trend tracking over weeks — which is what temperature data is most useful for — both devices produced comparable pattern data. The difference in absolute accuracy matters less than the consistency of the trend, and both delivered consistent trends across the testing period.
The Tempdrop native app displays temperature readings on a simple chart, confidence scores, and a note-logging feature. It lacks the data depth of Oura or Garmin Connect — there's no sleep stage data, no HRV, no trend analysis beyond the temperature chart itself. For users who want to do anything substantive with temperature data, the recommendation is to export to a third-party app via Apple Health.
Kindara is the most fully-featured companion app for Tempdrop — a dedicated cycle charting app that accepts temperature data and adds symptom logging, pattern visualization, and statistical analysis. The Tempdrop + Kindara combination is the most complete temperature-tracking setup available without the Oura Ring's price tag.
| Feature | Tempdrop | Oura Ring 4 |
|---|---|---|
| Temperature accuracy | Good | Excellent (finger) |
| No fixed wake time needed | Yes | Yes |
| Other health metrics | None | HRV, sleep, HR, readiness |
| Third-party app support | Kindara, Apple Health, others | Apple Health, Natural Cycles |
| Price upfront | $129 | $349 |
| Subscription | None | $6/month |
| 3-year total cost | ~$129 | ~$565 |
| Form factor | Upper arm band | Ring (invisible) |
Tempdrop makes most sense for users who: want dedicated overnight temperature measurement without the cost of Oura Ring, have irregular schedules that make fixed-time morning thermometer readings impractical, already use a cycle charting app like Kindara and want to automate the temperature input, or want a single-purpose device with no ongoing subscription cost.
It's a poor fit for users who want comprehensive health tracking alongside temperature data — Oura Ring covers temperature plus sleep, HRV, readiness, and activity. For users who primarily want temperature data and nothing else, Tempdrop at $129 is the most practical hardware option available.