I spent $5 or so on Torque. I had to provide my own phone and Bluetooth OBD plug.
Then I came here and found out about the Ultragauge. $80, and I didn't have to provide any hardware. That's a plus, because I don't want my phone to have to become part of the car- it's my phone. Knowing now that non-phone based solutions exist, I wouldn't even bother looking at something for my phone.
Besides, I use Waze when I'm driving.
