I just ordered this device (29 eur + taxes and postage costs):
Specs are here: https://ruuvi.com/ruuvitag-specs/
Many wireless sensors use their own proprietary wireless protocol (or Zigbee etc.), because Wifi takes too much power and the Bluetooth signal is too weak. That makes them incompatible with mobile phones or PCs without an additional HW (a hub). RuuviTag fixes this by using a very good Bluetooth LE antenna, which has even a 1 km range open air (!). Here is quite an impressive video about that: https://www.youtube.com/watch?v=wRpW2KIPfVo
The device contains temperature, humidity, pressure, altitude and motion sensors in a waterproof package. You can just directly read the sensors via Bluetooth in the accompanied Android or iOS applications. You can set a notifications when a certain sensor value limit is reached etc.
In addition, its all Open Source, SW and HW, and as a result there is an active community around it
There is ARM Cortex M4 based MCU inside. You can wirelessly flash updates or custom firmwares on it over BT.
Some usage scenarios:
- Attach to your bike to notice if someone is moving it
- Put it in Sauna to see when it is hot enough
- Attach to the front door to get a notification if someone sneaks in
- Leave it in your greenhouse to observe the temperature and humidity
- Have it in your basement to early detect water leaks
- Observe the air condition in your bedroom during the night