Voice alone do not demand much bandwidth, but is very sensitive to latency. Checking email can be high bandwidth if some relative or colleague sends a binary file of some kind, but do not care much for latency. Still, i think the primary use is one of disaster communications. Like being able to call or message that one is safe or in need of help, and where one is located. Think of it like turning a phone into a digital CB radio, with the added ability to forward as needed.