You might try working with one of these:
DSC Wireless Door/Window Transmitter
My house uses these with it's security system for monitoring windows or doors. It transmits at 433 MHz. Basically it sends out a signal whenever the door/window opens, closes, or it senses someone taking the cover off it. It also says 'hello' to the receiver every 20 minutes so the system can tell if someone is jamming the Tx. Each Tx has it's own unique address. Whenever one of the above actions happens, it sends out it's address, along with data about what's happening. This should be fairly easy to listen to with a receiver built for 433 Mhz.
If you didn't want to try to decipher with a reciever, you could by the wireless module made by DSC for the security system and listen to what it says about the Tx's through the Keybus.