I just downloaded WhatsApp Messenger on my Android.
It is a Smartphone Messenger which replaces SMS. This app even lets me send pictures, video and other multi-media!
WhatsApp Messenger is available for Android, iPhone, Nokia and BlackBerry and there is no PIN or username to remember – it works just like SMS and uses your internet data plan.
Get it now from http://www.whatsapp.com/download/ and say good-bye to SMS.
Although it is pretty convenient to use, it still is not the solution to everything. I have this on my phone but I will still rather prefer to email anyway.
The things I do like about it are the ability to group text, send images or other forms of media instantly to everyone in your group. Since this uses your data plan, it allows you to text/mms people at any number around the world.
If you have already downloaded the app, let me know what you think of it.