In reply to jkarran:
> No, what would be the point! Unless it were voice controlled it'd deliver none of the benefits of leading with none of the benefits of a toprope.
I guess the main point would be it allow you to work steep sport routes without a partner - which a top-rope auto-belay can't do as you would hit the floor on the swing.
It would also allow you to practice lead falling without a partner, so keeping the fear of falling under control.
I can't see a use outdoors - you'd need special anchors set for them, and clipsticking and shunting works - but in the gym I can see it being very useful, as long as the mechanism for pulling slack is smooth enough.
Lead autobelays on a comp wall would be great for people who work shifts and can't train at the same time as their mates, or people who travel a lot and turn up at gyms where they don't know anyone.