Its starting to get to the point where a new cross platform messaging service comes out every month. Brent Rose @Gizmodo said it best in “we need another messenger app like we need extra nipples” but the apps do tend to be popular. The latest to launch is eBuddy XMS which has pretty much the same features as all the other cross platform messengers and is available for BlackBerry, Android, and iPhone though it also has a desktop web client. Its free which is important though personally I am more of a fan of their regular eBuddy IM client.
You can check out more about it at www.ebuddyxms.com