Perhaps an even cooler alternative is this:
http://www.pegasusautoracing.com/ProductDetails.asp?RecId=4793
The lap timer you've been waiting for! Displays official AMB lap times directly from the track's AMB timing system. DisplayIT is easy-to-read yet small enough to fit on a steering wheel. Easy to setup and easy to use. Simple two wire hookup. Just provide power from your vehicle's battery (9 to 14 volts), enter your AMB transponder number and you're ready to go. (You only have to enter your transponder number once).
Provides:
Official AMB lap times
Gap with your best time
Current overall position
Gap with car ahead (in seconds)
Total laps made in session
Time on track for session
If your race organization is using the latest version of AMB's Orbits 2 or Blind Apex' Kronos 2 timing software, the following additional information is available:
Overall position in qualifying and race sessions
Class position in qualifying and race sessions
More accurate info when Timing & Scoring edits results in real time