I’ve written the first proof-of-mistake crypto token on top of Ethereum. You can see it at http://www.lostethereum.com/
It’s basically a proof-of-burn substitute for users who mistakenly sent to the wrong address. It requires a web3 enabled browser, i.e chome with MetaMask, Parity, Mist, etc. This let’s the web interface seamlessly interact with the Ethereum network.
Let me know what you guys think.