Lifehacker Use a Raspberry Pi to Keep Track of Who's Home or in the Office Lifehacker The Raspberry Pi Zero basically scans for MAC addresses so you can easily see who's connected to a Wi-Fi network at any given point. That data is then displayed on a dashboard and you can even set it up so you get text messages when someone arrives

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Use a Raspberry Pi to Keep Track of Who’s Home or in the Office – Lifehacker