PGP providers are trying to stand out from others now-a-days in one way or the other with selling also android based pgp phones and an built-in otr chat app.
They provide features on mentioned smartphones in terms off otr chat based on the cryptographic algorithm Diffie-Hellman.
Because of a potential wrong implementation in the use of mentioned algorithm the information transmitted may be compromized as only Diffie-Hellman primes of 2048-bit or larger are strong enough.
PGP Sure® Better sure than sorry!
When conversations should stay secret!