If I could make these, I'd be a millionaire.
Or I'd at least be revered by my sweetheart forever. She gets toe cramps in the middle of the night on a regular basis. She wears socks to bed. She uses a hot water bottle, but has to keep her feet in one (awkward) position to keep them warm. So my invention would essentially be hot water bottles you can wear on your feet. They'd probably look something like Crocs.
If anyone wants to sink some capital into this idea, let me know. Seriously, we're going to make millions. And this will be the jingle for our product.
(thank you, Garageband loops.)