My little project this last week end.
I need to add a few rf433 oregon temperature sensors to be linked to my rfxcom + jeedom domotic box.
Unfortunately, these sensors (oregon THGR122N) are about 25€ (or 15€ using a cresta clone), not including shiping costs.
The whole thing uses less than 2ma when sleeping, and max 20ma when it reads temperature from the ds18b20.
Possible evolution would be to replace the arduino pro mini by an ATTINY85.
Here comes the wiring.