Speaking of hacked together RF toys, I picked up an IM-Me toy a few years ago just so I could play around with Michael Ossmann's "$16 spectrum analyzer". I was able to see (poorly) the transmissions from my wireless weather station with it.

http://ossmann.blogspot.com/2010/03/16-pocket-spectrum-analy...

There is also a five part series on Youtube talking about what else you can do with the IM-Me. It is pretty amazing and well worth watching if you have some time.

https://www.youtube.com/watch?v=WGU30mF_dgM