I want to make a device that can cryptographically authenticate time and space. Im thinking of something like a raspberry pi with a RTC and GPS that is using its key to sign data about its current time and position. It will also post the signatures to something like OpenTimestamps. The purpose would be as long as you trust the device you could capture the QR code it displays and verify some photo or video was created when it says it was, so you could prove livestreams are really live or that some video was actually taken at some time/place