Best non-track way to time 0-60?

[Jombi]

I've read a bit about a Dragy device and a VBox, which appear to be high-precision GPS based devices.   

Due to the high cost of the Dragy and Vbox's, I've been using just an OBD2 adaptor with an app called CarScanner.  I'm assuming it just hooks into the cars speedo and uses the phone's timer.  So I guess the question is, how accurate would the car's speedo be, and when does the CarScanner pick up the first "move", ie, is it giving a 1ft roll or is it just detecting the first speedo non-zero input, and I guess same questions for the gps devices.

Thanks,

--jim

[Nick Halstead]

Dragy is the industry standard for those who cannot make it to the track. 

The method your doing will give you a general idea. Dragy is a lot more credible.

Think of it this way,
OBD module= Hey the capitol of the USA is on the East Coast of the country.
Dragy= Washington DC is located at latitude 38.8951111 and longitude -77.0363693, in the northern hemisphere.