I kinda question the viability of gps speedos. I remember back in the late 1990's when the GPS signals were subjected to "selective availability"(deliberate limits to accuracy). I've also heard that the powers that be were going to change the system, and obsolete old gps receivers. If there ever was a national emergency, like 911, they would "turn off" the satellites availability to non military apps. Now maybe we are so past that point of common use, that that could not happen, I don't know.
