Reportedly, Blackberry messenger (BBM), a unique service offered only for Blackberry customers to chat or share things with other Blackberry users is to hit Android and iOS devices soon. There are third-party apps like WhatsApp messenger (Blackberry, Android, iOS and Symbian) and Kik (Android and iOS) that offers similar services that also supports cross-platform. This could be the reason RIM considered to come up with their own proprietary app that supports cross-platform.
There are lots of services for push email for other platforms that are Blackberry like but many users stick to Blackberry for their BBM services like photo, location and video sharing which will only be available in Blackberry devices and not on Android and iOS. People who have not tried BBM could try it on their Android and iPhone and buy a Blackberry device to get the full experience.
There could be one time fee to use their service but the pricing and time frame of the launch are now unknown. Android version may come out within this year.
(via bgr.com and image via Pocketnow.com)