TextSecure Private Messenger enables you to send encrypted text messages for free to anyone who uses the app. The great thing about it is that it can also send unencrypted messages to people on your contact list who don't have the app installed on their devices.
Lightweight and fluent: Unlike similar apps, TextSecure Private Messenger sets up quickly -- with just a phone number -- and then runs smoothly, using an interface that despite its beautiful design remains fast and undemanding on resources.
Nice sharing features: Apart from the ability to send group messages, this app also lets you share images and other media with ease, making your conversations more engaging.
High privacy: Every message you send to another user who has the app is encrypted. What's more, no messages and no group metadata are stored on the server, making this app a much more private messenger than most other communication apps for Android.
Occasional hiccups: Every now and then, an encrypted message you send fails to reach its destination; the other person only gets a "bad encryption" message. Also, expect minor group messaging errors like blank spaces when texting people who don't have the app.
Adding contacts not easy: The process for adding a new contact within the app could be streamlined, to make it easier for you to connect with new people you meet.
A viable alternative to mainstream messaging apps, TextSecure Private Messenger lives up to its expectations, proving to be a solid, reliable app. Whether you text all the time or only occasionally, this is a worthwhile app to have on your smartphone. It's fast, lightweight, and thoroughly enjoyable.
From Open Whisper Systems:
Using TextSecure, you can communicate instantly while avoiding SMS fees, create groups so that you can chat in real time with all your friends at once, and share media or attachments all with complete privacy. The server never has access to any of your communication and never stores any of your data.
Private. TextSecure uses an advanced end to end encryption protocol that provides privacy for every message every time.
Open Source. TextSecure is Free and Open Source, enabling anyone to verify its security by auditing the code. TextSecure is the only private messenger that uses open source peer-reviewed cryptographic protocols to keep your messages safe.
Group Chat. TextSecure allows you to create encrypted groups so you can have private conversations with all your friends at once. Not only are the messages encrypted, but the TextSecure server never has access to any group metadata such as the membership list, group title, or group icon.
Fast. The TextSecure protocol is designed to operate in the most constrained environment possible. Using TextSecure, messages are instantly delivered to friends.