Wireless digital hydrometer and thermometer that logs gravity and temperature live from inside the fermenter.
The RAPT Pill floats in your fermenter and streams specific gravity and temperature to the free RAPT app over WiFi or Bluetooth. This version ships pre-assembled in a red housing with the wireless charging coil already fitted — set it on any Qi charger and go.
Key points
- Live gravity + temperature — follow fermentation from anywhere; no drawing samples.
- WiFi or Bluetooth — log to the cloud directly, or via a bridge device to save battery.
- Wireless Qi charging built in — plus USB-C; no cable fuss.
- Accurate — ±0.002 SG and ±0.2 °C.
- Sealed & sanitary — double o-ring, no exposed threads, FDA-grade plastics.
App & control
Use the free RAPT app (Android / iOS) to view fermentation graphs in real time, set gravity and temperature alerts, build fermentation profiles, and remotely control compatible RAPT devices. In Bluetooth bridge mode the bridge does the heavy lifting — saving battery, improving signal through stainless fermenters and fridges, giving an accurate core temperature without a thermowell, and enabling gravity-based control triggers (requires a RAPT Fermentation Chamber or Temperature Controller, sold separately).
Specifications
| Accuracy | ±0.002 SG · ±0.2 °C |
| Temperature range | −20 °C to 60 °C |
| Pressure rating | 0–5 bar |
| Size | Ø37 mm × 125 mm |
| Battery | Rechargeable 18650 Li-Ion (EVE); Qi wireless + USB-C charging |
| Connectivity | 2.4 GHz WiFi / Bluetooth |
| Housing | Nylon 12 & POK, red, double o-ring seal |
Battery life
| Telemetry interval | Battery life |
| 60 min | ~1.5 years |
| 30 min | ~9.5 months |
| 15 min | ~5 months |
| Bluetooth bridge only | 2+ years |
What's included
- RAPT Pill (pre-assembled)
- Red housing (fitted)
- Built-in wireless charging coil
- Quick-start guide
Setup: Charge for ~24 h before first use to calibrate the battery. Update firmware over USB-C / WiFi. Online features need a 2.4 GHz WiFi network.
Pair it with a RAPT Temperature Controller and browse the rest of the Fermenting range.