The crews on the dam project still use Sonim phones, which are "virtually indestructible" and have a three-year guarantee, says Sanjay Jhawar, vice president for marketing and business development at Sonim Technologies Inc., San Mateo, Calif. Features include sophisticated microphones and speakers to render voices without distortion, even when cranked up to blast through loud noise on the jobsite.

Some models can be managed remotely and support a host of configurable features, including a "man down" service that generates a call from a monitor if the phone takes a sudden drop, as when a worker falls, and a "lone worker" button that can advise monitors when a person is working alone so they can be checked if they fail to cancel the alert in a timely fashion.