http://news.ycombinator.com/item?id=601648
In particular, such an app would help alleviate problems with repeated checking. The user would use the app to take a photo/video of something instead of checking it repeatedly (e.g., you locking the front door).
The photo/video would be tagged with the time and place.
To actually try to cure OCD, one might introduce a probability that the photo/video will not be taken. One can have this probability increase over time as the user's condition improves.
Another possibility is to delete the photo/video automatically after some time interval, which decreases as the user's condition improves.
This is something that I might actually consider building if there is sufficient demand.