Clarification: they actually sell the phones to a recycling company, and then use that money to purchase calling cards for the soldiers.  So no, you wouldn't need to worry about anyone accessing personal information that you may have on your phone.
It's an awesome program, and has a full Skimmel Seal of Approval ©.
--Skimmel    
            
            
            Skimmel
RP Marshal, Rules Marshal, Storyteller