WatchOS 1 doesn't really support video, although you can do some tricks with snapshots or animated gif.
That demo in the first watch release presentation was a security company, showing a garage camera, if I recall. That was a mockup, and not actually possible quite the way it was presented at the watch announcement. (More of a 'one day in the future we'd like to do this' presentation, by the Alarm.com/ADT guys, I think.)