Privacy
For Nocturnal on Mac, Windows and Linux, the phone page at nocturnal.tools/remote, and the Nocturnal iPhone app.
On your computer
Everything stays on the computer: settings, the battery history it uses for estimates, and its logs. It sends nothing to us. It only talks to the internet when you turn on phone control or phone alerts.
Phone control
Your phone and your computer talk through a relay, ntfy.sh by default or one you run yourself. Every message is encrypted on the device that sends it (AES-256-GCM) with a key that only your phone and your computer hold. The relay sees sealed text it can't read, and keeps it only for a few hours, so a sleeping computer can still pick up a wake. Each phone has its own key, and you can revoke any phone on the computer.
Commands include your phone's generic device name (for example "iPhone"), so the computer can list it. That name is encrypted too.
The iPhone app
The pairing key is kept in the iPhone's Keychain, on that device only. The camera is used only to scan the pairing QR code; nothing is recorded or saved. The last status you saw is kept on the phone so it shows while the computer wakes.
The phone page
The page stores its key and the last status in your browser's storage on that phone. It loads nothing from other sites.
Phone alerts
If you set an ntfy topic for alerts, Nocturnal sends a short notice there when an agent finishes or needs you. Those notices aren't encrypted, so pick a topic name nobody can guess.
Questions
Nocturnal is open source, so you can check all of this in the code on GitHub. Questions go to the issues there.