Kryptos is a premium iPhone applet to encrypt your phone calls, the company behind it is planing on launching Kryptos for Android in January 2011 and Kryptos for RIM (Blackberry) in February 2011. This encryption mobile phone applet is very easy to manage and it will provide you with sound secure voice communications for a very reasonable price, Kryptos will work over any network, including 3G, 4G and Wifi.
After the user has downloaded the Kryptos iPhone applet from iTunes on their iPhone he needs to activate the account with Kryptos. Each user receives an individual ID, calls using the Kryptos applet will be secured using peer-to-peer encryption, the initial symmetric encryption keys exchange is made using 1024-RSA and after that calls are routed with AES256 encryption.
There are no backdoors in this encryption applet, your encrypted conversation cannot be decrypted by anyone other than the two parties participating on the Kryptos call session and the company does not keep any logs of the calls made, your phone applet will keep a record of call logs locally but they can be easily erased.
Note: Kryptos is not free and it requires a monthly fee.