TomTop offers the Konnwei OBD II Bluetooth Car Engine Diagnostic Tool for Android in several colors (Red pictured) for $13.49. Coupon code "AK6202" knocks that to $10.49. With free shipping, that's the lowest price we could find by a buck. This device connects to your Android smartphone via Bluetooth 3.0 to display the real-time operating performance of your car. It measures fuel consumption, turns off the "Check Engine" signal, and downloads data to external media.

Note: This item ships from China and requires two to five weeks for delivery. The countdown timer on the product page does not reflect an actual expiration time and resets daily.