[zelly]

How would the contract know that the job is completed? Ethereum contracts can only access events on the chain itself. There is no way to go out to the network and, say, ping the new Pi, because there is no way to cryptographically verify that this happened. So some off-chain server somewhere has to issue a command (with some private key) to the contract to say, "Yes, I checked that the work was done, you can disburse the funds". In which case you never needed the contract anyway and just could have sent the money directly.