Rather than straight out "off the shelf" devices, wouldn't they be better served by something equivalent to a Panasonic Toughbook. Maybe that could be covered by 3rd party cases (with built-in batteries) but an iPhone is something that requires a bit of protection even for everyday use.
Well the military guys choose 'laptops' (!) like these:
Funny is, it is considered to be 'light'.
BTW these things are sold to NATO members army high level personnel only. Don't try to buy like a friend did
While on it, it comes with Windows.
A military MD we know keeps buying these.
Of course as Ericsson did some AOL thing with Sony, they don't produce anymore. You would be really surprised at some 'package not opened' prices for that old phone. So why he keeps buying? Even that monstrous phone can't stand to field conditions in peace time.