Liiiyuan Speedometer HUD， GPS Digital Speed Meter with MPH ，Head Up Display for All Cars, USB Cable Plug & Play

I have only had this for a few days, but it works well. Once plugged in, it takes a minute or two to find the GPS signal and then display the speed. While driving, the speed is pretty accurate when compared to the car's speedometer. The display is clear and easy to see in sunlight. I plug it in to a USB port connected to the car stereo, so when the car turns off, the device turns off too. Since it uses GPS, it needs to maintain its signal which it does while on the highway/roads etc., but it can lose its signal when you enter a multi-level parking garage/tunnel, etc. If you just need a speedometer only and no other readings, this is a good way to go.

I meticulously installed on my motorcycle. It powers up fine but only registers 0 mph.

It is supposed to turn off after some time of no movement and then automatically come on when it detects vibration/motion. It's plugged into a cigarette lighter adapter that is on all the time. After 30 minutes of sitting idle, engine off, the display is still on. Other than that, it does work well.

Ford F150, works right out of the box. Bright, accurate and very reasonably priced.

Pros: nice and visible/readable, accurate, quality housingCons: if your vehicle power port has power all the time, you will need to wire this to an accessory power feed or unplug it each time you turn off the car... not an issue for my van but could be an issue for some vehicles.