I purchased an FM Radio transitter from the local electronics store. It ran from a 9V battery. I modified this devide by changing the input (microphone) to the jack. By selecting a specific pickup combination allowed me to turn the transmitter on and off. I set it to operate at a specific frequency on the FM band on the radio.
The end result was I did not need an amp to listen to my playing. Listed to my guitar through the radio on my stereo, and if I wanted to I plugged in headphones.
A big positive with this is you have a cordless connection to the radio.
If you go down this path make sure there is a channel available on the FM band that wont interfere with other signals.
Cheers
Steven