I've seen similar before and there's a guy who lives locally who has a recumbant and uses something like this.
I do have a couple of concerns though... watch the vid and it seems to "fish tail" quite a lot at speed (apparently 2 wheeled versions are more stable, though I would think they are harder to turn)... the other issue is making sure that nothing comes into contact with the rear wheel, you'd be amazed how quickly things can wear through just with a little friction.
Personally, (from what research I've done in the past) I think I'd go with something that either has a platform or some kind of cradle, a bit like
this. Always fancied one for when I'm diving off the islands in britanny. Just for a laugh I'd love to attach one to an
A-Bike