Dream Land. Do you mean a "a simple GPS with ground speed read out"???
I mentioned in an earlier post that I started carrying with me a hand held GPS unit on my flights a year before I retired. Had to use an external antenna to get a signal. It was attached to a suction cup which was placed on the side window. It was interesting to see the ground speed within 1 knot of the aircraft computed one. This simple unit would have saved the lives of many pax and crew in the past had they been available and used. It has all you need to safely do an approach, GS, track and true (not pressure) altitude. Long live GPS.