I'd be interested in them, but then again I should just get glasses that change, or start wearing my contacts again so I could actually wear sunglasses.
Anyway, back to the contacts, the transitions lenses have gotten to where they change fairly quickly, though over time they may not be so great. You might look a little odd outside, but once indoors they would change pretty quickly. As for time, make them in 2 week disposables and you wouldn't have to worry about the lens change time slowing, though getting it cost effective is probably the trick, like nodle said.