Does your console look like this? Id make a small plate to fit in this spot and delete the tray. Mount them there. The pillar under the deat belt is a good idea too. Let me just say ive fished wires the the door boot before, while the rears were easier than the fronts, it was still not fun.
I saw this on amazon https://www.amazon.com/Dorman-628-040-Universal-Seat-Heater/dp/B002U6IL9O/ref=sr_1_1?s=automotive&ie=UTF8&qid=1324943932&sr=1-1&tag=vs-auto-convert-amazon-20
And theres plenty of sites like heatedseatkits.com
I would look to the back side of the center console for mounting switches. When i get to my truck at the end of my shift ill get a good look back there and see what other ideas i have. You would need to either run wire from the fuse box or find a suitable line to tap into. Personally id run its own wire. Mostly because i dont know what would be okay to tap into.