Login password
Auto-unlock needs your Mac login password. It is verified by the system, then stored in this Mac's login keychain and read only when unlocking. It is never uploaded to iCloud or anywhere else, and you can delete it in Settings at any time.
Bluetooth and pairing
Your iPhone and Mac talk directly over Bluetooth, exchanging only one-time nonces, signal strength and signatures. The iPhone's signing key is generated in the Secure Enclave and cannot be exported; the Mac stores only the paired device's public key.
Camera and photos
Photos are taken only when someone uses your Mac while guard is on. They are stored locally on the Mac first; if you confirm it's you with Touch ID within 20 seconds, or your phone comes back, the photo is deleted immediately.
Events that are not cancelled are uploaded — with the photos, Mac name, trigger and time — to the private database (CloudKit) of your own iCloud account, so they can be delivered to your iPhone. Only your Apple ID can access the private database; the developer cannot read it.
Deleting from Photo History on the Mac removes the local photos; deleting from Alert History on the iPhone also removes the record and photos from iCloud.
Remote commands
[Lock now] and [It's me] on your iPhone are written as signed commands to the same iCloud private database. The Mac verifies the signature, carries it out, and deletes the command.
Logs
Both apps keep a local debug log of connections and distance decisions for troubleshooting. It stays on the device unless you export it yourself.
Update checks
The Mac app uses the open-source Sparkle framework to check for updates once a day. It only requests the update feed on this site (aethernative.com) and sends no device or usage information. You can turn automatic checks off in Settings.
Deleting everything
Unpair on both devices and delete the apps to remove local data and the keychain password. iCloud records can be deleted from Alert History on the iPhone, or under System Settings → Apple Account → iCloud → Manage.