Maybe not super privacy-related, but a neat security solution if you need to monitor SSH logins to some box:
This sends me notifications as soon as anyone logs in to any server I manage. The reason I created this solution was because I need to grant access to the privacytools.io servers to a few choice people, either for maintenance when I’m away or other reasons. But I’m also not a trusting person, so I want to make sure these people don’t get their SSH keys stolen or whatever and let some attacker wreak havoc. Or just generally I don’t want a matrix.org situation to happen to us!