Last night, I dreamed of a Japanese vending machine that did not sell things, but instead purchased toys and figurines from children, particularly the collectible sort.
It would be hard to do that for real, as the value of such toys depends on the exact model and its condition, obviously. But we’ve already got machines that ‘buy’ used soda cans and bottles for recycling. What else could a vending machine reasonably buy?
Jon Lasser 
Isn’t there a coinstar-like machine that buys gold jewelry by weight? I vaguely recall hearing something like that, and it would be plausible for any precious metal that could be confirmed by density and maybe resistance, then measured by weight.
Another plausible, if not necessarily practical, idea would be composting machines that pay you for biodegradable waste, compost it, then sell fertilizer. You could maybe use x-rays to confirm the input is organic?
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