What's needed is more cryptography. Build keys into sensors to sign media and use something like blockchain to broadcast the signature at time of capture / time when the device returns to the internet.

Won't be perfect, but it would be a hurdle. Also, for things like audio and video if you know the location on the planet then there are certain artifacts that are hard to fake with mere AI. The way sound bounces off walls in a room or shared environmental noise that other devices in the area would detect, like a plane flying by.