Tom Tom or Garmin. The best also show the prevailing speed limit, your true speed as well as the presence of speed cameras. Tom Toms even squalk when you go more than 10% over the limit in the area you are passing through. Any GPS device that shows your true speed against the prevailing limit and can be situated in your line of site is far more more likely to promote road safety than something that automatically restricts your speed and might get it wrong due to a mapping error or a cloud. Imagine filtering into traffic on a motorway at 60mph then suddenly having your speed restricted to 40mph.