The blockchain! For something like file storage, you can use cryptographic techniques to prove that a party is or isn't holding the data that they were contract

The blockchain! For something like file storage, you can use cryptographic techniques to prove that a party is or isn't holding the data that they were contracted to hold. This doesn't expand to the physical world well (for example, how can the blockchain measure whether or not you damaged a rental car?), but for digital resources like storage, certain types of computation, and digitally owned assets, loans, etc., you can use blockchain arbitration.