[GadgetKen]

Originally Posted by liquix

He has already dismissed sat phones because of the call quality. He is not too interested in satellite phones because of the loss or reception indoors.

Think an Iridium phone rental may make sense for your internal client when visiting Nepal or Tibet because of roaming agreement issues. Because they work differently from traditional phones, suggest he tries test calls and text messaging from your office parking lot before he flies off somewhere.
Iridium voice quality can be very good under if you are outdoors with no structures interfering with line of sight to the satellites (got compliments on the voice quality on an Iridium voice call from a tropical island a couple of weeks ago). Text messaging will often work indoors if you are near a window, and voice will work indoors in the upper story of a wood frame structure (ideally near a window). There are also small magnetic patch antennas and adapters available that enable use of an Iridium phone inside a vehicle or a building.