How to build a wireless lavalier microphone?

I would like to build a wireless lavalier microphone for my DSLR. My camera shoots HD video and has a 3.5 audio in jack. I have a lavalier microphone that takes a 3.5 jack. I would like to find some cheap(ish) transmitters and receivers (preferably light and small) so that I can shoot and get good quality audio. The transmission range need only be 10 feet but more would be great. 
Does anyone have any ideas?