Be careful with them.....
A buddy of mine owns the best upholstry shop in this area - (does all the restorations, etc) and was telling me the other day that he's constantly doing warranty work on heated seats, even new ones - primarily because of the new seat construction. He had one in the shop and told me that the main reason they go bad is a wire breakage due to putting your knee on the seat. The older seats were better built (had real springs) and this wasn't a problem. So if you get heated seats - Don't Do That... ...