I use Destinator1 (
http://www.destinator1.com) for my Viper. It works with your PocketPC (assuming you have one) and provides voice-guided door-to-door directions. It costs $329 and includes the software, North American maps (NavTech map data - considered the best and used by Hertz and many other car GPS systems), and a 12 channel GPS receiver.
I actually wrote a product review on it that is pretty detailed. Check it out here:
http://www.planetpdamag.com/content/062602tk.htm
The beauty of this setup is that it plugs into your cigarette lighter and charges both the GPS (mounted on dash) and the PocketPC at the same time and it's completely portable. I switch the unit from car to car all the time.
I would be wary of some of the Garmin products. They make good stuff, however, from what I understand on several of their products you have to pre-plan your route on your PC and then it will download the corresponding "map slices" to the Garmin device. This is due to a limited memory capacity on the Garmin products. I believe it has built-in city-to-city mapping via major highways, but if you want door-to-door directions, you need to perform "map slicing" on a PC and then download it. This is probably true of most GPS systems under $700.
That's why the really good GPS systems cost $1500 or more and require like 6 CD changer or a single DVD drive to store the map data.
Also, the lower-end Garmin products don't do turn-by-turn voice-guided navigation.
The Garmin GPS V is a decent product. It has city-to-city directions, and you can get door-to-directions by downloading one of 7 U.S. map zones (slices) from the CD they provide. So for example, the Northeast is a complete zone. It's a B&W screen though. So not exactly the coolest product for a Viper.
The Garmin Colormap StreetPilot GPS is the "color" model you see at the Sharper Image (and Brookstone I think). Since the screen is color and looks really cool, they push this product a lot.
But read the "fine print":
"The StreetPilot is designed primarily for the automobile and contains a world reference map showing Interstate, US and State highways, plus rivers and lakes in the US, Canada, and Mexico, with main arterial streets shown in metropolitan areas.
Optional Datacards can be programmed for street level map detail and access to business listings and points of interest in your area."
The data cards essentially mean you need your PC to download door-to-door directions! This is bad. Who wants to remember to boot up their PC and pre-plan their trip?
That's why I like Destinator1, I never need to download specific maps to my GPS device. They compressed the detailed door-to-door maps so compactly, that I can load the Northeast and Western New York into about 64MB which I store on my PocketPC's CompactFlash card. They have a patent on the compression I believe. With my 512MB CF card, I actually loaded the entire U.S. map onto it. Oh yeah, it has Points of Interest too, such as Gas stations, Restaurants, etc. I really like the "find nearest" Gas station feature. Especially when driving in the boonies in the Viper. That fuel needle sure moves pretty quick!
I also bought the "optional" Universal PDA Mount with Flexable Arm Bracket
which uses a suction cup to mount onto the winshield. I get lots of compliments and questions on my mounted PocketPC.
So for the cost of a PocketPC ($300-$500) + $329 for Destinator ($600-$800) you can have a small, portable, GPS system.
If anyone takes this advice and likes their GPS setup, just let me know. I'd be curious to see if you love it as much as I love my GPS. I use it all the time! Maybe i'll use my digital camera and post a picture of my setup here.
