As a former user, I offer this information. The Iridium system is the only real choice for the casual user. Phones are running around $1000 to $1500 on the web, some with a few pre-paid minutes. After the pre-paid minutes expire or are used, the basic plan cost $40.00 per month, and around $1.30 per minute for outgoing calls to any place in the world. There are plans available that include paid minutes. The Iridium system has it's own "country code", like 1 for the US, so when someone calls you, they pay for the call at what ever rate they would pay for making a international call. The one feature I used more than anything was the free incoming text message. Folks can send a text to your handset from the web site for free. The system will hold the message until you turn your phone on. I used it as a way to get me if you really needed me kinda thing.
The quality of service is quite different than cell service. The satellites are low earth orbit, so they are moving around you. Your call is handed from one satellite to the next as they fly past your location. The voice quality is fair at best, and as mentioned above, subject to your surroundings. Being in the bottom of a deep valley will be problematic.
In short, they work, but are not a replacement for a cell phone. They are not cheap. I would look at options for increased cell coverage first. Motorola is making bag/vehicle mounted phones again for all carriers. A 20' pole and a directional antenna might get you service where the low power, personal phones don't work. Further, you might look for small regional cell carriers in the area you will be in. They sometimes offer service in areas the major carriers don't. Not all towers provide coverage for all phones. They are carrier specific. Just because your phone from home does not work, does not mean there is no service available.
Another option might be a satellite internet setup. They take a little time to setup at camp, but add a magic jack and a cordless phone and create your own cell site with email and web. Verizon currently has, and ATT is coming out with, femtocell boxes. They use your broadband internet connection to provide service to your cell phone where coverage is poor. A web search will tell you more about that.
Jeff & Cindy
'09 27FB Flying Cloud
'91 350 LE MH