[jwalton]

The thing is though, at least in the US and Canada, the law explicitly says you can swap out parts in your car with third party parts, and auto makers are not allowed to void your warranty.

A heated seat is really just a coil in the seat you feed voltage through, and it gets hot. So if you find the input to that coil, and find a 12V rail or run a line from the battery, you can install a little rocker switch to power the heated seat, and there’s nothing the manufacturer can do to stop you.

[codefreeordie]

This would all work today, though if it became a trend, manufacturers could start adding vehicle integrity checks into the power-on sequence that would refuse to start if modifications are detected -- and if they had the first-party components use cryptographic signatures to authorize themselves, DMCA would then step in and make circumvention probably criminal again.