Mack,
If you Google "Automotive GPS Speedometer" you'll get a wide array of offerings. There's also a GPS driven unit to feed just about any electric speedometer (if you already have one?), but it's in the $200 range and is a 6"x6" box plus hardwired antenna - Auto Meter My question, I know that they use the latest high speed GPS interface and look at multiple satellites for accuracy, but how do they do if you get in areas where the "view" of the satellites is compromised, like heavy tree cover, heavy cloud cover with storms, etc?

Mike (CHR ), does your unit have any type of remote antenna that needs clear view of the sky as opposed to being in the dash, surrounded by metal/fiberglass?