I recently watched a SGII in "like new" condition go for $120... not cheap enough for starving students!
What about the PLX kiwi MPG?
PLX Kiwi MPG - MPG Meter, Trip Computer, Engine Check Scan Tool, OBD2 OBDII Gauge
Here it is on amazon:
Amazon.com: PLX Kiwi MPG Trip Calculator and OBDII Scanner: Automotive