Seed Cipher allows you to encrypt/decrypt your crypto wallets recovery phrase with a password and it will still fit into the usual crypto metal plate formats, adding an extra layer of protection to your hard earned bits!
If you intend to store it on a metal plate that is later kept in a safe deposit box for example you still might run the risk that somebody opens that box without your authorisation. This app allows to add an extra layer of protection. To ensure no data is leaked the app is sandboxed and not allowed to make any network connections etc. Ideally you would run this on an iPhone in Airplane Mode and then wipe the device for maximum security :-)
Warning:
Please note it is not safe to store your recovery phrase on the cloud or any other internet connected device like your notebook! The used encryption might not withstand well designed brute force attacks etc. If you want ideal security use AES256 to encrypt your whole seed phrase and store the result in safe way (will not fit a crypto metal plate though).