Maybe someone has a really clever idea but I do not think anything rooted in the real world can work. You will always need some kind of sensor to record whatever it is that you are doing in the real world and you will have to prevent people from faking those sensor readings. If you had a central authority as root of trust you might be able to build some tamper-proof device that provides cryptographically attested values but I can not think of a way to do something like this without already having a root of trust.