Is there's any chat programs like BBM but for ipad useds only

I, I'm wondering if there's any application like blackberry messenger but for iPad users only?

I've never used BBM but in iOS 5 there is a built in iMessenger App which I believe is similar.....but I'm sure that someone will tell me I'm wrong....

Check this link out http://www.apple.com/ios/ios5/features.html#imessage

Thanks

AppPack from cydia.