I can sniff the air and know if you are near.
Your phone’s wifi system transmits periodic “pings” in search of connection points. Those pings contain a set of numbers unique to your phone — its MAC address, or media access control address.
And I can see them.
Normally they look like 12:34:56:78:90:ab, but I’ve blocked out most of these, which are the unique IDs of my neighbors’ and my devices. The ones ending in 9, though, are from my phone.
I’ve known this was possible, and even did some sniffing with my laptop using a popular program called Wireshark.
But for this week I got a similar system running on a Raspberry Pi with a USB wifi antenna. And I refined my searching technique to make an efficient, portable detector.
What could one do with this data? I think a lot. In Austin’s airport, the number of pings flying around, each representing roughly one person, helps determine wait times at security.
I have a couple of ideas of my own — all good, no evil.
More on that, and details about how I got this far, in a future week.
#MakeEveryWeek is a challenge to myself to do just that for all of 2015. The original post on the idea is here, and the running list of projects so far is here.