We've been working on some powerful iOS developer tools powered by Ghost PII. I open by talking through why you might want to do this: I posted a video yesterday on Meta’s headaches moving data from the European Union to the United States and this sort of a technology is a way to avoid this problem by making sure that data is never in plaintext anywhere but on the end user's computer.
My colleague Jack Phillips will help you peek a bit under the hood at how all of this works, including showing just what (securely encrypted data) will actually be stored in Firestore (just what we happen to be using in this case) and teasing a bit about the next phase in which we build some analytics that work on this data directly without need of encryption.