it occurred to me as I pondered the previous day's LJ on my way to work this morning that green date stamps or tear-off notes or anything else of that nature are all fundamentally the same solution as the webcam; an admission that you *don't* remember locking the door and need some tangible/visible evidence that you did. so although they might be more fun/interesting ways of remembering than the "ordinary" webcam solution, they aren't your request of being able to solve the problem in your mind. to that end, I think your singing solution may be as good as any...