I have one of these if you are interested .
DL90 is Race Technology's entry level GPS "black box" data logging system. Put in the simplest terms, it stores a range of vehicle data for later analysis on a computer - the system does not include an in-vehicle display. Can be used at most track days to log data which is viewed "after the event".
Cutting edge features of the DL90 include: High accuracy GPS, digital accelerometers, 90 minutes logging time, 2 analogue inputs, 1 digital input, RPM input, wheel speed input.
For further details see:
http://www.race-technology.com/WebPage2/Products/DL90/DL90Introduction.html