After buying 2 cheap dongles and having one warrantied twice, (car would die and theft light would start flashing), I bought one that is about $25.00 and it has worked well (except for when I thought it had finally went out and I just had my bluetooth turned off).
The Dash Command app has the ability to put in your vehicle parameters, (gear ratios for up to 6 gears, final drive ratio, engine size, tire size)
The app is free but to do the vehicle specific pids it is $10.00 and you have a login so that it saves.
If you go on dashxl.net, you can get a lot of different interfaces/skins, I currently run the Regal interface/skin, and I switch back to the stock skin when resetting trips and logs, you can also check and clear most computer codes, I even reset a seat belt light code once
Adapter:
New BAFX ELM327 Bluetooth OBD 2 CAN V1.5 Scan Tool Android OBD Reader / Scanner | eBay
--- I have found the app to be about 2-5% off, about normal of even factory gauge instrumentation.