This looks pretty cool (particularly that it's easy to use). If you're already using AWS you could just use nitro enclaves to do this directly, but this makes it easier to use, and easier to use if you're not using AWS but trust AWS (+ evervault, particularly for availability). It's cool to see this for something other than just payment card info vaulting.

Biggest problem I could see with applications is that if you were using this inside a larger application, someone with control of the application could just change the less-secure application to bypass Evervault entirely. Wouldn't compromise historical/data-at-rest data already inside evervault, but would bypass it for new submissions. That doesn't mean this isn't useful, but it would be a concern in some use cases.