WhatsApp Messenger, the popular messenger for smartphone, has been updated for Windows Phone to include new look and new features.
WhatsApp 2.9 now has a lock screen notification option. Your chats are backup every 24 hours. And new LiveTile design.
WhatsApp is a cross-platforms messenger (Android, iPhone, Nokia phones, Windows Phone, BlackBerry) uses 3G or WiFi to send free message (text, picture, audio and video) with your family and friends.
WhatsApp for Windows Phone is free for the 1st year and $0.99/year after that.
[source: Windows Phone Blog]