speed check gadgets

[Guest]

Hi guys
Anybody got any good information of where I can obtain gadgets which
tell me (not where speed cameras are...)but how fast I'm going?
My GPS (before I lost it in the Grand Erg Oriental in Algeria in 2001)
gave me an incredibly accurate speed of within the error rage +/- of
0.25- 0.50 kilometre.
I obviously don't want to pay an absolute fortune, but I would like
some information on these kinds of things.
Gratefully yours
Renate