Oh I hadn't considered pulseIn(), that a good idea (my poor wallet, lol) I've been looking around the forum for making a speedometer and I'm noticing a lot of people hit issues with max speeds. I'm not a pro, but I do get up there in speed from time to time.
So for testing accuracy I was going to literally get out my tape measurer and mark out 100' on a nearby hill and do laps up and down it. Then I was thinking I could go to a nearby track (alternatively, I would use a football field) and do some laps around the track. That should give me a good measurement for a hill and a flat track.
That has definitely been the least accurate one I've tested with so far. Now admittedly, maybe the problem is with me, their documentation is a little spartan on how you're supposed to use things, but while I've been duly impressed with the accuracy of the GPS reading, the odometer has not been wowing me. It's definitely designed to only be mostly accurate while in motion.