ChatSecure allows for encrypted messaging through popular messaging services such as Hangouts, Facebook, Jabber and more. The app is free to download and use with zero in app purchases.
Orbot plugin required to make it completely secure.
Pro Passed EFF's security review
To pass EFF's security review ChatSecure had to encrypt data in transit, the encryption had to be end-to-end, the app needed to provide forward secrecy, app's source code has to be open to independent review, users have to be able to verify contact's identities even with the service provider compromised, app's cryptographic design has to be well documented and app's source code has to have been audited in the last 12 months.