I purchased an "ELM327" from ebay for $14. It is bluetooth tethered to my GS3 with Torque (free version). It also paired with my Alienware M18X laptop and the software that came with it.
It read fast and accurately. Reset the error codes after I did my repairs, and it has been the best $14 I have spent on my car.
Ebay Link
Ebay seller wowpartspro