There is IOTA, which is technically proof-of-work, but there are no "miners" validating large blocks of transactions like with Bitcoin. Each person creating a n

There is IOTA, which is technically proof-of-work, but there are no "miners" validating large blocks of transactions like with Bitcoin. Each person creating a new transaction in the Tangle validates two existing transactions and does a small bit of PoW, and by doing it this way, there are no fees. Early in the project there was even an effort to create a different kind of specialized processor like you mention, something low-power that could be used in the wild in sensors and whatnot.