The EcoRoute
HD comes with an OBD2 dongle that sends the car's engine data via BlueTooth to the compatible NĂ¼vi navigator device, so in theory the data should be just as accurate as with the ScanGauge.
It can also show and reset engine error codes.
Description:
Garmin ecoRoute? HD : Be your own mechanic - monitor your engine and save fuel
Here's a review:
Garmin ecoRoute HD Review & Rating | PCMag.com
Looks tempting.