It's very do-able, but unless you can modifiy most boot-loader firmware & sometimes the PC
side software, you'll need a set of RF modules with true bi-directional capabilites, and a way
to reset the target so it can jump/vector to the boot-loader routine on reset.

See this project: http://www.rentron.com/PicBasic/wireless.htm

I did this for a client several years back, and it's still ticking.