[DaveTN]

Great question! I was looking for an app for almost the same reason. I have just finished restoring an older motorcycle and used modern all electronic gauges on it. I had to modify the speedometer interface to make it work but have not been able to accurately calibrate it other than driving next to someone else and pacing to measure my speed.
With a small suction cup mount on my fairing for my Mogul and TGPS, it should work great.
I had thought about asking this question months ago and never got around to it.

Thanks,

David