Nice project! I'm working on an automotive Arduino-based project so am interested to see what others are doing. (Maybe we need an automotive or telematics forum/thread?)
Question: How are you powering the Arduino? I know that since most cars use a nominally 12v electrical system, theoretically it should be possible just to route this into the Arduino's power plug. However, the "Practical Arduino" book notes that the actual voltage in auto electrical systems can vary much more widely and suggests using a separate power supply with its own regulator. How are you handling this? Thanks...