WhatsApp Messenger is available for iPhone, Android and Windows Phone, and yes, those phones can all message each other! Because WhatsApp Messenger uses the same internet data plan that you use for email and web browsing, there is no cost to message and stay in touch with your friends.
In addition to basic messaging WhatsApp users can create groups, send each other unlimited images, video and audio media messages.
WhatsApp is also available for: Apple iOS, Windows Phone and Windows/Mac PCs.
No hidden costs: Once you and your friends download the application, you can use it to chat as much as you want. Send a million messages a day to your friends for free! WhatsApp uses your Internet connection: 3G/EDGE or Wi-Fi when available.
Multimedia: Send Video, Images, and Voice notes to your friends and contacts.
Group Chat: Enjoy group conversations with your contacts. Add or Remove group participants, change group subject and set a group icon.
Personal: Set a profile photo which will be shown to all your contacts
No international charges: Just like there is no added cost to send an international email, there is no cost to send WhatsApp messages internationally. Chat with your friends all over the world as long as they have WhatsApp Messenger installed and avoid those pesky international SMS costs.
Say no to pins and usernames: Why even bother having to remember yet another PIN or username? WhatsApp works with your phone number, just like SMS would, and integrates flawlessly with your existing phone address book.
No need to log in/out: No more confusion about getting logged off from another computer or device. With push notifications WhatsApp is always on and always connected.
No need to add buddies: Your Address Book is used to automatically connect you with your contacts. Your contacts who already have WhatsApp Messenger will be automatically displayed under Favorites, similar to a buddy list.
Offline Messages: Even if you miss your push notifications or turn off your iPhone, WhatsApp will save your messages offline until you retrieve them during the next application use.
And much more: Share location and places, Exchange contacts, Custom wallpaper, Custom notification sounds, Landscape mode, Message timestamps, Email chat history, Broadcast messages and media to many contacts at once, and much much more.