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 multimedia!
WhatsApp Messenger is available for Android, iPhone, Nokia, Windows Phone 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!