The concept, put very simply, was a wrist mounted slingshot (or catapult, as it's apparently called here in England). It would have mechanical features, of course, but the way it fired was the same as a slingshot. I'll show you a picture of it, so you can quickly get an idea of how it was supposed to work.
But alas, this picture is as far as I got with the project. The problem was that the only elastic band that was strong enough to be able to fire something a decent distance was too thick and cumbersome.
However, this new version of the project is definitely going to work!
Probably.