I recently got my hands on a HW-6915. They come with the TomTom street
navigator as standard, with one free map. The GPS is reasonably
accessible, and as the gadget runs Windows Mobile 5.0 and Java it ought
to be programmable enough to do most things.

I tried out the GPS capability in London, in a moving car. It takes a
while to acquire an initial fix, but once locked it worked quite well
for an "urban canyon" environment. Well enough to show the change from
an un-numbered slip road to the highway as we went across the white
line.

That obviously sounds ideal. There is a MiniSD expansion slot, and as
cards are available up to 2GB capacity in this format you could load
those nice freeee raster charts the USG gives away on them. (Using
something like a
href="http://www.gpsinformation.org/dale/PocketPC/pocketnav.htm"this/a)
The screen is of excellent quality, but you will have to think
carefully about where you put it to read it reliably despite the sun,
as with any LCD device.

BUT. Another GPS function out of the box is to assign a geographical
position to photos taken with the integrated camera. I tried this out.
The photo software (HP Photosmart) includes the option to look up these
coordinates on Mapquest. I tried this out, too. Nasty surprise -
position showed something like 5 miles east of true! I'm not sure
whether this was the GPS (I don't think so as it was tracking the map
accurately), HP Photosmart or Mapquest's fault.

Another issue is battery life. Operating the GPS receiver continuously
seriously drains the battery. This could be a serious problem, although
if you're out of cellular (triband GSM/GPRS/EDGE) coverage you can save
power by shutting off the cellular radio. Alternatively you could run
it in its charger cradle, tho' it wants AC power. (HP may sell a 12VDC
charger, but I dunno) It's tempting, remembering the chap on another
thread who's using a wireless LAN to interconnect his laptop, GPS,
echosounder, autohelm, wife, etc to think that you could link it to
other devices using its own WLAN radio - but using this and the GPS at
the same time would be genuinely battery critical.

The cabling provided with it ends in a USB plug, but note that the
socket on the device is not a standard USB port - nor is it a standard
mini-USB port - it is something peculiar, so you will need to use the
cradle if you want to connect any other gadgets to it like that. As you
can pull power into it from the USB port on your PC (or whatever) there
is really no reason not to do it that way.

It's a cracking product, far better designed than any other
PDA/smartster I've encountered. But watch the battery life, careful
with that Mapquest, and think carefully about how to use it practically
in your cockpit - its list price is £400, and it would be very easy to
drop overboard.