This iPhone controlled Mazda RX-8 by Jonathan Oxer takes the cake. Using a wi-fi connected iPhone the user can connect to a computer in the car which is connected to the Net using a separate internet connection. With this setup the user can now open doors, start the engine, monitor all of the car stats such as RPM, temperature, fuel tank, and if that isnt enough you can even see where the car is on a Google map.
The cars webserver provides a password-protected web interface optimised for full-screen display on an iPod Touch or iPhone running the SOPOD full-screen browser. The web interface has three screens: 1) Control, which provides a top-down view of the car with buttons for start, stop, lock, unlock, accessory power, and boot release; 2) Telemetry, which displays real-time data acquired from the engine management system such as RPM, vehicle speed, coolant temperature, throttle position, etc; and 3) Location, which uses a Google Maps mashup to display the current location of the vehicle on a map using current GPS data.