In short, BBM is run through the BlackBerry system, and is compatible with no others.
Might try Yahoo IM, there is a RIM version that uses push technology and can be used without ruining BlackBerry battery life, that's how I chat with my Iphone friends from my BlackBerry.
Posted from my CrackBerry at wapforums.crackberry.com
hi thanks for the reply - I am in australia so there is no unlimited SMS option. I only ask, coz at the moment i use BB. and most of my friends (who are in USA, Singapore, around asia basically) use BB too. So msging them thru BBM is the easiest way for me. I was thinking of switching to iPhone if there was an app that could retain this function. I can modify the iphone to work with a BB plan. but seeing the iphone has no PIN - i dont think there would be a way. might be wrong though.
Ya, it is not possible unfortunately. Using a 3rd party IM client and communicating over that will be your best bet. Just tell all your BB buddies to sign up for and use a free messenger and get yourself either beejive or ebuddy to chat with that all you want SMS free.