As you all may have guessed my current project is with automobile telemetry. I currently have a working accelerometer prototype and am looking to include other sensing capabilities with it.
Right now I'm eyeing temperature and pressure senders that are purpose built for in car gauges. Any idea how you think these work? They are relatively cheap and made to be screwed into the oil pan of a car. I can get an oil temp sensor for anywhere from $17 to $70 (http://www.egauges.com/eg_sType.asp). I don't think a circuit could be to difficult to make to have one of these work with an arduino.
...for the curious the previous two posts I was working on a boost (turbo pressure) based trigger. So i am wiring up a MPX4250AP ($15 pressure sensor) (0-36psi) to the arduino and then triggering an event (in a 12V system; hence the relay post) when a certain pressure is met. I'll also display the pressure and allow the user to control the pressure trigger point with a pot.