The powersupply for the Garmin is more or less weatherproof ( http://www.kawasakiversys.com/forums...ead.php?t=5571
) but the GPS itself (now a Nuvi 1450) and its connector are not.
I have a weather resistant PDA bag (Bag Connections from Twisted Throttle) that I use if I'm sure of hitting a lot of rain, I remove the whole assembly and just use the GPS with the bag.
Otherwise, if I'm just caught out in a shower or I want to run the cammera on my smartphone, I use a clear dry bag that slips over the smartphone cradle and GPS that still allows me to shoot pictures and videos.
Like the GPS powersupply, the smartphone is running off a 12V-5V USB "weatherproof" powersupply that is weatherprooof up to the connector that plugs into the cradle/phone-neither of which is water resistant.
This is the 12V/5V USB unit available for many vendors, I got mine here http://burnsmoto.com/usb-power-socket-weatherproof.php
If you want to use the USB powersupply to run a Garmin GPS, you need a special USB charge only cable, normal USB cables will put the GPS into mass-storage mode and make the GPS think its connected to a computer.
I'm experimenting with 3 different sizes of clear weatherproof mapcases to reduce the bulk of the drybag and have a flatter surface on the face and camera side. Might end up cutting one down to get the best fit.
When parked outside, I use a small black drysack to cover the whole assembly -keeps it dust and waterfree and is out-of-sight-out-of-mind to passerby's.
After 40,000 miles I haven't lost a GPS yet.