This is another intractable problem with blockchain and cryptocurrencies, known as "the oracle problem" - in order to do something useful in the real world, it

This is another intractable problem with blockchain and cryptocurrencies, known as "the oracle problem" - in order to do something useful in the real world, it has to interact with the real world in some way. There are various schemes to try to offer solutions for automatable processes, but when human decision-making is involved data still has to come from humans who are "off-chain", i.e. have no direct link with the blockchain or cryptocurrency platform.