I agree with /u/na85. If you're worried about law enforcement or corporations sniffing keys out of your devices RAM, you have other things to worry about besides "what app should I use for communication"?
If you're seriously worried about communicating without trusting your phone, then you either need to find communication devices you do trust, or else look into verifiable TRNGs [0], dumb serial printers that can be directly attached to RNGs [1], and either manual encryption/decryption algorithms [2] or one-time pads.
I simply want real privacy, not an illusion of one. It's pointless to use any half-baked privacy approach when your device is compromised by design; who knows if the current mainstream becomes dissent in 20 years and people will be hanged because of their old communication logs? Thanks but no thanks.
