visit P H Andersons web site, he sells a pre-programmed 'kit' that will interface many Dallas 1-wire temperature devices to a serial Port.
The kit I'm referring to here is the 512 Point Temperature Measuring system.
Click here for more details about what this kit is and the serial data stream it sends out.

There is also a 256 point temperature and A/D kit, but that requires the 'PC' (i.e. the empeg) send 'requests' to the Pic and the pic responds with the reading.
But it can be used to control 1-wire switches.

Note: both of these are kits of parts, plus instructions, you still need to make up the circuit either on breadboard or Veroboard or similar. He doesn't provide PCB's.

He sells (some of) the 1-wire devices as well, along with lots of other useful kits.

One of these kits would be a cost-effective way to get a few temperature readings from the various parts of your car into your Empeg via the serial port.

If you live overseas, he will post to some overseas countries (but not all), and he takes VISA etc, and I think PayPal.

I recommend you look and see what's on offer here. Maybe you find a good alternative that with a little hacking on the Empeg will do what you want.