csipsimple supports zrtp 

On Wed, May 9, 2012 at 4:21 PM, Aaron Zauner <azet@azet.org> wrote:
i'm also still following this, but it seems to be a dead end.

off-topic:
current smartphones already have the capability to run sms[1]/voice
encryption software or voip with encryption [2].

[1] https://github.com/whispersystems/textsecure
[2] https://play.google.com/store/apps/details?id=com.privategsm.beta