are there any other products like the iPAQ rx5915? (GPS/PDA w/ wifi)

[ra]\\[dom]

From top of my head I can only think of Nokia N95 which has GPS built in and has lots of other features.

Next option would be a separate GPS receiver (they come in small sizes) with Bluetooth support and then some kind of handheld computer that you like where you install the software for navigation. Might be a bit more expensive, but its most customizable.