There’s no sign-up or approval required to use the feature. When you tap the icon to initiate a call with one of your BBM contacts, BBM will ask whether you want to make a voice call or try a video call with the beta feature (provided your contact is also eligible to participate).
This feature was made available to US and Canada only in early May while still in its beta stage, and now BBM users in Africa and other countries (but not all)can now make video calls on their Android or iOS devices.
Android: OS 4.4 (KitKat) and higher
iOS: iOS 8 and higher.
Although this feature has been available in latest BB devices Blackberry just decided to include it in forgotten Android and iOS users