I recently got a i737 blue bluetooth GPS receiver from
http://www.semsons.com
I have been using GPS systems for nearly 10 years and this is by far the best unit I've had.
It is extremely sensitive and locks very quickly.
I've currently been using it with my Treo 700wx (Sprint) with Telenav, Google Mobile maps, and Microsoft Live Search.
I also have used it with my IPAQ Hx4700 with GMM, MSLS, Co-pilot live, and Anywhere MAP.
This provides great flexibility by being able to use it with multiple systems.
I currently have the bluetooth patch from the verizon 700wx loaded(hannip). This bluetooth stack is FAR FAR more stable than the native bluetooth.
I've used this stack this with:
stereo-A2dp (multiple headsets) works great!!
DUN(will lock up the treo under load ie a bandwidth test - but only locks up occasionaly with sling box)
Hands Free (HF) - Plantronics Voyager 510 (best) and motorola hs-850
Serial(GPS )-i737