This idea is part of the A Dollar Worth of Ideas series, with potential open source, research or data science projects or contributions for people to pursue. I would be interested in mentoring some of them. Just contact me for details.
Similar to Passable Shots this is an app to gather information in the phone that can only be decrypted using a private key that is not stored in the phone.
In this case, the information stored is a counter. Using homorphic encryption, this counter is stored encrypted with a public key stored in the phone and 'kept updated' without decrypting.
The use case for such an app is rather tenuous but it could be used for keeping track of the number of security cameras in an area, for example.