Aaron Coolidge writes:

As an almost total aside, I got my Globalstar GSP-1600 satellite phone today.

The big limitation seems to be that the antenna has to be perfectly vertical,
with a clear view of the sky. It does not work inside a house, or in a car.
Presumably it could be used in an airplane if the phone were on the
glareshield.

Others have had better experiences with Globalstar equipment.
http://skyhelp.net/field_trial.htm

--kyler