Recording and projecting images in three dimensions.
We've seen it in the Imaging Suite, which is fancy hospital equipment, and in two bars; once as a window, (opening scene of The Train Job) and once for playing pool (opening scene of Shindig - Management Not Responsible For Ball Failure). It can't be too expensive, so why don't we see it more? [How do we know that it isn't all over the place? We only notice it the two times it messes up, we could easily assume that it is just working fine the rest of the time]