There are times when you will be off-grid (camping, disasters, remote location work, etc). You could use satellite phones to stay in touch with your team but that can get costly very quickly. A company called BearTooth claims to have built a smartphone sleeve that turns it into an FRS style radio that uses unlicensed bands to communicate (it seems to convert your cell into a high priced software controlled FRS radio).
It will allow you to have voice conversations, send text messages and send your geolocation information.
The company claims it will have similar range to "normal" unlicensed band style radios (which means it should work over a couple of miles depending on the terrain). The magic is encased in aircraft grade aluminium and contains the radio and battery. The company says the device will will be controlled by custom built software that will be available for both IOS (iphone) and Android (Samsung, HTC, Nexus, etc).
It will be available "sometime" next year and pricing hasn't been announced yet. You can checkout the company's website for more information (link).