http://www.camaro5.com/forums/showpo...52&postcount=1
Read this post. Every time I took a vid and matched it with the iPhone, it was within .1 and never more than seve one hundredth. (.07)
Not saying it will be EVERY time but the answer is most of the time it's accurate within a tenth.
If you do 10 runs, you'll be within a tenth on average.
Make sure you set it up right and mount it or wedge it correctly.
I don't care what anyone says, it's a good tool to measure your acceleration. The dyno part blows, and the top speed is inacurate. On mine anyway.