Hi Tony
Why not interface a simple temperature sensor circuit through the serial port?. The temperatures could then be displayed in a hijack app.

The advantage of this method is that you could set Hi and Low temp warnings and play a sound file. You could even have it play a sound file when the ignition was turned off that said ....hope you've got something warm wrapped around your ......(insert plural anatomy feature here). Its %^&* cold out there.....

Peter