Cheap GPS Digital Speedometer
Not to be confused with full sized GPS speedometers -- which cost a lot more -- these are inexpensive (typically about $50 US) digital readout speedos.
Some people buy them to replace a broken speedo, or to know their actual road speed after a tire diameter change. We bought this one off Amazon to use in our sprint-race Ghia as a second opinion on our calculated tire sizes & gear ratios. It does require the selection of a few options.
This model is the Kingneed C60, very similar to others in its price class, and features an auto-brightness projected HUD (heads up display) option as well as the more prosaic ability to read directly off the LED screen. It has lots of other features, such as KPH or MPH display.
The display also shows elapsed driving time (from power on) and has a speed alarm preset. For instance, you might preset to warn if you exceed 70 MPH if using this on the street.
There is no calibration. Just plug it into a USB charger such as the kind that sticks into a cigarette lighter, Velcro to your dash, and the device will detect the satellite signals in about 60 to 90 seconds. We got detection in under a minute.
The instructions warn the operating temps are up to 70 C. (194° F). that error is between 1 to 5 % at a steady speed, and bad weather can affect operation. Testing on a rainy day at various road speeds, we had no satellite connection problems, but did notice accuracy was erratic at speeds below 15 MPH.
FJC
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I use it all the time in my non vw bug vehicles, its completely free and only permissions it requires is GPS, so make sure you download the correct one. 
