iGap is a FREE messaging app for Android and other smartphones that uses your phone's Internet connection (4G/3G/2G/EDGE or Wi-Fi, as available) to let you message friends and family. It is one of the best messaging apps for Android. IP has a clean interface and a modern design, and it is very easy to use.

You can add your contacts from your phone book or from your iGap chat history.

To send a message, just tap on the contact you want to message and then tap on the message button.