I happen to have a spare iPAQ, older model, that I setu p for just this
purpose with an inexpensive Compact Flash GPS unit. After some looking for
software I selected iGuidance from iNAV. They only sell softwar. They will
work with generic CF GPS units as well as serial interface unit, like a
simple Garmin. They offer 3-d perspective so the display looks like you are
driving down the road (most of the current version s/w packages do this).
If the unit is on and looked in, you simply select "Input a destination",
specify you want to input Lat/Long, it thinks for a minute of 2 and plots
out the map from where you are to there. Pretty simple, very
straightforward. One feature they didn't advertise that I have found nice,
if you miss a turn or head off in the wrong direction, it will recalc the
route to get you back on track. If there isn't an alternate route, it will
holler for you to turn around and go back.

I got a RAM cradle and ball mounts from Cumulus Soaring and have it mounted
on my Dash so I can see the screen with only a breif side glance from the
road.

I haven't had to use it for a retrieve yet, but I think I'm all set. I
really set this up so my wife can find me. That will be the test of how
"simply and straight forward" it really is.

John Scott