QuickMSG

QuickMSG is a secure messaging format and an Android App of the same name. With it you can send messages either to other contacts directly or to groups. Its aim is to combine the ease of use that messaging apps give with the security of encrypted email.

QuickMSG uses a number of existing technologies and combines them such that the user can send messages to contacts and friends.

There are a few differences with most messaging services:
There is no central QuickMSG server or infrastructure.
Your messages will be sent via the existing SMTP/IMAP E-mail infrastructure.
Your messages will be sent using encryption from end to end. Nobody in between can read it.
QuickMSG uses well known and established PGP encryption. By default QuickMSG will use 2048 bit RSA encryption for each message.
You identify with an email address, not with a phone number. QuickMSG is thus not bound to a phone, but can be used on other device types as well.

There are also some differences with regular email:
No subject. The subject is not really needed for 'quick' chatting. Besides it isn't encrypted anyway.
Easy to setup. Encryption is the default. No need to jump through hoops to setup PGP.
Easy group handling. Groups are easy to create and are synchronized to the members automaticly. They can be used the same way as any other contact.