Idea for nostr! Delayed sending after user is inactive

Imagine you can delay sending an encrypted DM indefinitely until the user is inactive for some period of time (i.e. does). This can be used for inheritance schemes on crypto. You send a private key to people you want to inherit your digital wealth, but relays keep the message without showing it to recipient while you continue using nostr. If a relay doesn't see any new messages from your npub for say 6 months, it shows the message to the recipient.

This can be implemented as a new feature in the message - keep it secret until the sender becomes inactive