It takes a photo of whoever uses your Mac while you're away, whether you left it unlocked or they know your password, and sends their photo to your iPhone if the face isn't yours.
I built Someone Was Here as a menu bar app making use of Apple Vision and a local face recognition run via Core ML. It all runs locally on your Mac with no tracking or ads.
Real-time remote alerts are available via one-time $4.99 lifetime purchase via the free companion iPhone/iPad app, Pushover, ntfy, Telegram or a webhook.