For measuring the Temperatures in the various parts of the house and outside i use Oregon Scientfic Temp/Hygro Sensors. They work on the 433 MHz frequency and can be received with my RFXCOM receivers.
Oregon Scientific THGR238
Oregon Scientific THGR122NX
I also use 1-Wire temperature sensors from Dallas Semiconductor. They are connected to my HA7Net.
1-Wire DS1820
This one is used for the swimming pool:
Oregon Scientific THWR288