It uses a TMP36 to read temperature and it is optimised for power consumption.
It uses watch dog that wakes every 8s and increments a counter. Once the counter reaches a certain value (e.g. equivalent to 1 hour), it will read and send temperature to the gateway.
Every 12 hours the voltage is also read and sent.

According to the battery life calculator, a cell coin battery with a capacity of 200mAh should last for ~ 3 years, given that:

Current consumption of device during sleep is 4.5uA
Device wakes up every hour
Current consumption of device during wake is 10mA
Duration of wake time is 1000 ms