MetroBuddy Secure SMS is a free app for the Android phone to send and receive secure SMS messages in between individuals or groups, the other end will need to have the app installed and be in your contact list with the country code number, even if you are both in the same country, to be able to interact together. After launching the app a secure connection in between phones is established you will see the message “Adding contact“, this involves exchanging up to 8 SMS messages and could take a few minutes depending on mobile phone carrier.
You will know communications are secure when you see a closed padlock next to your buddy’s name, from then on anyone eavesdropping on your messages will only be able to see random data, the user does not have to do anything else other than typing in a normal SMS message.
You can let other people known about this app using “Tell a friend” from the main menu this will send a download link to your contact, it is possible to create a group and send a single message to everyone at once. I couldn’t find any information in the developers website about the encryption technical details but the way the app works I would say that the messages are not encrypted themselves it looks as if a secure encrypted tunnel in between phones is created, similar to HTTPS (SSL) in your web browser, and anything that goes through it is secure.