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Origin Story

Once upon a time, I went on a vacation and asked a cat sitter to look after my cat. I didn't hear from the cat sitter for a while, and started wondering if it was possible to tell who and when was visiting my cat at home. I learned that most phones broadcast their unique MAC addresses over Wi-Fi, and that a small system-on-a-chip can capture their probe request messages. With that knowledge, I decided to build a scanner along with a service to help answer a simple question: is it (my cat) fed?

Once I had a scanner up and running, it started reporting probe requests from many devices nearby. In fact, there were seemingly too many, and to separate the signal from the noise, I started looking for the daily patterns. Soon it became clear there were a couple of phones, a Samsung and an LG, if I recall correctly, that would appear every other Wednesday in the morning: those were likely the gardeners. Some other device would also appear regularly same day every week: possibly, a garbage truck?

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Frequently Asked Questions

Q:Do I need to plug the Micro-USB cable into a computer?
A:No; the cable is used to power the scanner, and you can use a USB charger, or a USB port on some appliance, such as your TV.
Q:Does the scanner require a Wi-Fi connection?
A:Yes; the scanner continuously uploads the data to the cloud, and for that it needs an internet connection.
Q:Does the scanner work offline?
A:No; it accumulates too much data to store locally, and providing the user experience from a system-on-a-chip is an engineering challenge.
Q:Can I download the information in e.g. CSV format?
A:Not yet; that is on the product roadmap, though.
Q:If I have several scanners in different locations, can I identify the devices that are active at one and then at another?
A:Yes, but with more manual effort than we would like. Please reach out with your specific use case, and we will look into that.
Q:What are the green circles with letters on them on the screenshots?
A:The letter pairs, like Mo, Tu, are the weekdays of the last week. A green circle means the device was active nearby on that day; no circle means it wasn't. You can tap on that calendar to see the detailed activity information.
Q:Why do the hearts have different colors on the screenshots?
A:The colors are assigned randomly when you label the device as a favorite. The colors help you see the familiar devices in the potentially long list of the devices nearby.
Q:Where do the device names come from?
A:There are several sources, including the SSID names for the routers and DHCP packets from the devices on the same network. You can specify the name yourself, too, by tapping on the pen icon. The screenshots have artificial names for illustration.
Q:What is the blue bar on the screenshots?
A:Blue bar shows the relative strength of the Wi-Fi signal from the device at the time. The longer the bar, the stronger the signal.
Q:What is meaning of the icon next to the device name on the screenshots?
routerWi-Fi access point, such as a router or a hotspot.
smartphoneWi-Fi station, such as a phone or a notebook computer, from a known manufacturer.
device_unknownA device from an unknown manufacturer, or a randomized MAC address.
Q:I have another question; how can I get an answer?
A:Please send an email with your question to