The free app allows you to save 2 documents (each having 2 scans). I thought it will be a good testing point if you really want to use this app. If you have any ideas, don't hesitate to share them. The roadmap can be seen in the proofpocket.com at the bottom. Please keep your private stuff safe :)
Proof Pocket - Secure offline document storage with biometric encryption. Scan, store and protect your important documents with Face ID, Touch ID or master password. Everything stays within your phone.