A way to lose three stone without moving, of course!
I'll second that! Especially if we can add not having to live on rabbit food exclusively.
An invention I would dearly love (it's actually already been invented but only by, and for, one person - never to have been repeated) and that is a water-powered potato peeler. My friend's Dad invented it for his wife as she hated peeling potatoes and other root vegetables.
To look at, it was like two large mixing bowls that separated in the middle but the top one had a large hole in it to drop the potatoes or veg through. The inside was lined with something like sandpaper. Water was fed into the 'thing' by a small pipe fixed to the kitchen tap. The water made the inside of the 'drum' rotate very fast so that the sandpaper type stuff took the skin off everything and all peeling done in seconds!
Any GNs who can reproduce this - you have one customer here already!