lets you put a hotspot over any object in a video. The hotspot will then track the object on screen (quite reliably in my tests) and add text or a link.
I have used it to imagine that an old (but very funny) video
is being used in a vocational course for crane drivers. I'm sure other C2.0 members will think of better examples.
(BTW I was unable to embed this - has Ning removed that feature, or am I just being inobservant?)