For those who never owned a blackberry, bbm is like sending text, audio, or pictures through a messaging client on blackberries server. It used only your data connection, 100% free unlike sms or mms, and everyone with a blackberry had it. It also gave you notifications when the person you sent it too received it AND when they read it. It was always on, never required you to sign in and always pushed. Anyone who had a bb misses it. Pingchat is the closest thing to bbm that I have found, and it is across all thee platforms (although it still kinda sucks on a bb). You don't realize how nice it is to get the notification when the other person receives your message. Pingchat will put a check mark next to the message you send when the other person reads it.