Instead of deleting the secret on trip, and requiring a re-arm, it could instead derive a new secret on trip, by e.g. hashing the previous secret. That way you don't have to manually re-arm it, and you get a record of all trips.

Say e.g. a bug walks in front of the camera, tripping it. Then 1 hour a later an evil maid comes in and tampers with the system. In my design, you could look at the photo record, see that the 1st trip was a false alarm, then continue looking at the data, and see that the 2nd trip was something real.

Compared to with the current design, the bug would trip it, then you would get no record of the actual evil maid. You would see the photos of the bug tripping it, and think "oh, it's just a false alarm, I don't need to worry", and trust the computer, even though it's tampered with.