Sorry to say, but I do not think that there is an easy (or hard) way to do this. Like a prior poster pointed out, to get heated seats requires A. an overhaul in the wiring B. fillaments put in (which requires taking the seats into an upholster). This is not to say that it can't be done, but it is more work and $$$ than I willing to throw towards it. I did take some pictures, so if you would like I can post them.
"Happiness is found in owning a BMW, bliss is is found in modifying the heck out of it!"