The ultimate envelope prediction. The ultimate card to impossible location.
A prediction is clearly in view inside of an envelope window. It could be a note, a playing card, a bill, or billet.
It can then be switched - undetected, seamlessly, and invisibly. The spectator can be burning your hands and they still won't see it happen.

Imagine this:
Your audience sees a playing card inside of the envelope window, in full view the entire performance. A participant selects and signsANY card, then it vanishes completely from the deck. The one card that has been in view since the very beginning is taken out of the envelope - in the fairest way possible and it is THEIR signed card.

Or imagine this:
Multiple random spectators name anything - destinations, activities, numbers - and everything is revealed in a prediction that's been visible the entire time.