I use an iPAQ 3800 with an expansion sleeve and a CF card GPS (Teletype).
I use the free GPS-LOG software. By using a sleeve, I have 2 batteries
available. I have successfully gotten 4 hours of time on just the internal
batteries. I keep the backlight turned off. My primary use to date has
been as a logger so I can review fligths later. However, I am beginning to
use this setup for navigation and in-flight information. Using the GPS in
the sleeve, there are no wires to deal with.

If neccessary, an external battery could be made with 4 rechargeable NiMH AA
cells that would significantly extend the time. They could be connected to
the same connector as the AC recharge adapter.

I had tried the Velcro-to-the-leg approach. I encountered some problems with
this approach. The primary problem was it was much harder to see the screen
quickly and easily. The second was when flying a 1-26E, I had a difficult
time with maintaining GPS signal with the GPS reciever on my leg and down
inside the fuselage. Finally, at times it was hard to get sufficent light on
the screen to enable it to be read.

I purchased one of the simple RAM cradles from Cumulus Soaring for the iPAQ
and Sleeves along with the the 4" suction cup kit. This holds the iPAQ up
next to the instrument panel where it is very easy to glance at the screen
for data. I use the 1" balls for the arm ends. These seem to have good
grip and don't slip. I've fastened the suction cup to the canopy of both a
1-26 (for 3 hours) and a 2-33 with no problems. I find this solution vastly
superior to the having it strapped to my leg.

I liked the RAM cradle and arms so well, that I bought a second setup for my
tow vehcile. I used a ball bolted to the dash in place of the suction cup.
This holds the iPAQ near the steering wheel where it is easy to take a quick
glance at the display for map information. I use this set up for road
trips, but also use it with the GPS-LOG software to pratice flying tasks to
learn to use the in-flight software in an environment where I can pull over
and stop if I need to figure something out.