Keep in mind that this group isn't led by just any person, but Phil Zimmermann himself (creator of PGP).
It should be noted that the idea of cryptographically secure telephones is pretty old. Back in the 90s, there were some projects like ZRTP and PGPfone to establish VoIP and telephony cryptosystems, but they never caught on.
I don't know how this will fare. The fact that it's Android-based and doesn't use an OS built from scratch worries me.