The Vuforia VideoPlayback sample is available for Android, iOS and Unity. However, depending on the specific platform used, certain restrictions may apply.
Videos can be played on-texture (i.e. video is rendered as a texture attached to the trackable in 3D space) on devices running Android 4.0 (ICS) and above.
On Android versions prior to 4.0 (i.e. on all 2.x and 3.X versions), videos can only be played in fullscreen mode; the sample code already contains logic to automatically detect the Android version and to select fullscreen automatically if needed
Videos can can also be streamed from a network URL (e.g. "http://myorg/myvideos/video.m4v"); on Android 4.0 and above, videos streamed from network can be played on-texture without problems or limitations (same as for local video files).
Videos can be played on-texture on any iOS version supported by Vuforia (no specific limitations).
However, videos that are streamed from a network URL can only be played in fullscreen mode on iOS.
In general, the same constraints as for Android or iOS apply, depending on the target build platform chosen.
In addition, the fullscreen mode (as implemented in the sample) makes use of a specific API (Handheld.PlayFullscreenMovie) which is only available with the Unity PRO license (not available on Unity Android Basic).