Encrypted cell phones

Everyone has a cell phone these days, essentially a small portable computer with a display. It is a shame that we do not regularly have end-to-end encrypted communications. There is no excuse not to. At the very least, one can start with encrypted text messages. Public keys may be exchanged via bluetooth (or infrared) if meeting in person, and the display can be used to read aloud key signatures to each other; assuming one trusts each other's voice, it can effectively thwart MITM attacks.

I feel one of the main reasons for this failure is that phone companies selfishly keep everything closed.