Phone software encrypts your voice conversations

Voylent is a program that runs on your cellphone and encrypts your conversation before sending it out over the wireless data-channel in the GSM network. Normal GSM conversations are only weakly encrypted and can be easily sniffed; Voylent aims to provide robust encryption to prevent eavesdropping.

Voylent is a client for GSM cellphones that encrypts voice conversations (IP support not available in this version). We have just released our first public beta and are looking for testers, feature requests and feedback. The client has been tested only a few models, mainly Nokia S60 with Symbian OS. The full list of devices it runs on is included in the release notes & FAQ.

Link (Thanks, Rodolfo!)