Here is some infos about an OMG compatible Door sensor mainly interesting by the fact it send a signal for open status and a different signal for close status of the door.
When the AAA battery is low it sends also a signal continuously (every 3s and the led blink), I encountered it when the battery was at 1V.
When sending signal (open or close) 30mA during around 1s
Sleep current 27uA continuously
AAA battery capacity is 1000mAh
4 sending per day -> 4* 30/3600 = 0,033mAh per day for sending
Sleep current per day ->0.027mA * 24 =0,648mAh per day for sleep
Total per day: 0,681mAh
1000/0,681=1468 days -> around 4 years
Power consumption when no action