The Personal Blog of Stephen Sekula

Finding Fitbit

I’ve been sick all week. The moment I arrived in Michigan for the MCTP Second SPring Symposium on the Higgs Boson, I started getting a scratchy throat and running a fever. By the time I made it to my hotel and made the round trip the the nearby CVS for some TheraFlu, the body aches had set in and I could feel the warmth in my chest growing – an early indication of much coughing to come.

So, when I arrived home from the conference for the weekend I was very much looking forward to being comatose on the couch for most of the weekend. This morning, however, we had some drama that took my mind off the coughing and the hacking. Jodi walked into the living room and said, “I can’t find my fitbit. I had it when I went running, and I noticed it wasn’t in my pocket when I was mowing the lawn. I don’t know where it is.”

A manual search commenced, with the both of us slow-walking around the back yard in rows. Our search turned up nothing. We also poked around the house in obvious spots, but found nothing.

I tried to find the fitbit’s wireless signal with my mobile phone and a wifi signal strength application. But, a quick search on Google revealed that fitbit uses a proprietary short-range wifi network called ANT+, which standard mobile phone antennas are not tuned to receive.

That left one last option: using the fitbit’s own limits data syncing base station in the hunt. The station cannot tell you the signal strength of any single fitbit connection. But, it can tell you whether or not the fitbit has synced recently. Since the fitbit syncs just about every 15 minutes, one needed to only place the antenna in location, wait 15 minutes, and use that to establish a radius in which the fitbit cannot or can be located. The range of the fitbit wifi signal is 15 feet. We only needed three positive syncs in different locations to get a general triangulation of the fitbit.

The map below indicates the data. Green dots mark locations where the antennae successfully received a syncing signal from the fitbit. Red dots indicate failed locations.


Sure enough, in the overlap region of the three gray circles we found the fitbit, sitting on a shelf just out of view in a closet. The fitbit had been removed for a change of clothes, and then promptly forgotten. This was a sweet and simple use of technology and a little physics to help in the hunt for a small lost gadget.

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