I got the idea for this from Morrowind.
It would be cool if you could craft a new type of lock, a "Trapped-Lock" or something, that you can use on chests. Having a Chest equipped with this would not keep it from being opened, however, if you try to open it without using the key it will spring damage to you based off the purity of the iron used to make it or something.
There would be no indication if a chest was trapped or not, so each chest would be a gamble.