[tedmiston]

A multi-person key is interesting.

In practice, however, any system like this, Snapchat, etc is easily defeated with a USB cable and QuickTime's record device screen feature. I suppose it could be useful to others depending on your "threat model", but generally it offers no protection from a savvy computer user after you've unlocked it once.

Edit: Not sure why the downvotes. This is completely correct and you can test it yourself with any iOS app. I've added more explanation to clarify.