1. Text Secure (play.google.com)
TextSecure encrypts your text messages over the air and on your phone. It's almost identical to the normal text messaging application, and is just as easy to use.TextSecure provides a secure and private replacement for the default text messaging app. All messages are encrypted locally, so if your phone is lost or stolen, your messages will be safe.Messages to other TextSecure users are encrypted over the air, protecting your communication in transit. TextSecure is the only Android private SMS/MMS messenger replacement that uses open source peer-reviewed cryptographic protocols to keep your messages safe.Rather than simply pretending to hide your texts by putting them in another place, TextSecure uses cryptography to ensure that they remain truly secure.
2. Red Phone (play.google.com)
RedPhone provides end-to-end encryption for your calls, securing your conversations so that nobody can listen in.RedPhone uses your normal phone number to make and receive calls, so you don't need yet another identifier. Use the default system dialer and contacts apps to make calls as you normally would.RedPhone will give you the opportunity to upgrade to encrypted calls whenever the person you're calling also has RedPhone installed.RedPhone calls are encrypted end-to-end, but function just like you're used to. Uses wifi or data, not your plan's voice minutes.
Second place must-haves: Tor apps Onion Browser (Apple iOS) and Orbot (Android), or running your own VPN.
Both Onion Browser and Orbot make use of the Tor Project, but they each function slightly differently (with privacy protection limitations falling on the Apple side of the tree due to the closed nature of iOS).
3. Onion Browser (Apple iTunes)
Onion Browser is a minimal web browser that encrypts and tunnels web traffic through the Tor onion router network and provides other tools to help browse the internet while maintaining privacy.Websites do not see your real IP address. Your connection is encrypted before it leaves your device, providing protection against snooping by ISPs or people who share a WiFi connection with you.Tunnel bypasses restrictive firewalls: you can access the entire Internet from behind ISPs or corporate connections, or when inside countries that practice online censorship. Access websites on the "dark net" of anonymous .onion web sites, only accessible in the Tor network.User-Agent spoofing: hides the fact that you are using an iPhone/iPad from websites you visit. Ability to block third party cookies or all cookies. Can change IP address and clear cookies/history/cache in one button.CHINA/IRAN NOTE: Due to online censorship techniques using deep-packet inspection (DPI), this app does NOT currently function in China or Iran.
4. Orbot (play.google.com)
Orbot is a "proxy app that empowers other apps to use the internet more securely. It uses Tor to encrypt Internet traffic and hide it by basically bouncing through a series of computers around the world; it is the official version of the Tor onion routing service for Android.(...) instead of connecting you directly like VPNs and proxies. This process takes a little longer, but the strongest privacy and identity protection available is worth the wait.Use with Orweb, the most anonymous way to access any website, even if it’s normally blocked, monitored, or on the hidden web. UseGibberbot with Orbot to chat confidentially with anyone, anywhere for free.Orbot can be configured to transparently proxy all of your Internet traffic through Tor. You can also choose which specific apps you want to use through Tor.Any installed app can use Tor if it has a proxy feature, using the settings found here. Check out our fun, interactive walkthrough.