Kuzaranda is a Skype-compatible feature-rich SIP client for the BlackBerry Playbook developed by Eugene Fafel. SIP is an cross-platform protocol for voice, video calls and IM.
I prefer these cross platform solutions to the 1st party video conferencing all the mobile platforms provide now. Kuzaranda can place SIP calls to compatible clients on iOS, BlackBerry, Android, Mac and PC. Users can also place calls to mobiles, landlines as well as connect to Skype users.