The app is called photo tlock. It is $9.99 in the app store.
It stores a photo for one minute up to one year, in minute increments. It required an Internet connection for the time base, so no cheating.
You can use a realtors lock box, set the combo, without looking at it, take a picture and store it. Close the lock box and you are stuck until time expires. It has a pass code to override if you like, or turn it off for more excitement.
I have used it regularly and it works great.
Have fun!