Anyone on here who has an iPhone or iPod Touch should check this app out....its called Rev. There is only a lite version of it now which only tracks acceleration and GPS. Once the full version is released you will be able to see vehicle speed, RMP, fuel consumption, engine coolant temps, fuel pressure, calculated engine load, throttle position, intake manifold pressure, air intake temp, timing advance, mass air flow, fuel level, barometric pressure, EVAP pressure, and more.....all in real time on the phone.
They are going to sell something that plugs into you OBD II port on your car (no OBD I support) with a wireless transmitter attached to it, which connects to your iPhone or iPod touch.