Trevor has recommended WhatsApp Messenger for the iPhone which will soon be available for BlackBerry’s as well which will allow cross-platform messaging.
“WhatsApp is a direct iPhone-2-iPhone messenger chat application. WhatsApp allows you to carry on a conversation in real time with your contacts without having to pay for SMS.
In addition to chat there is a “Status” feature, thanks to which you and your friends will always know what’s up and how to best get in touch.
And with iPhone Push Notifications, WhatsApp can even let you know when your contact’s status changes and what they are up to.”
