Podcast: Why there were 56 OT vulnerabilities this week – Stacey on IoT


First, I commend Greg for knowing the difference between “occupancy sensor” (someone is in the room), “presence sensor” (Greg is in the room), “motion sensor” (something moved in the room) and PIR sensor (something hot has just passed through the detection field of the sensor). Cheer!

While I agree with Kevin and Stacy that much better and more interesting occupancy sensors will probably be available in about two years, there are now other options available that might help depending on the case. exact use. I’ll limit this to discussing options that would work with HomeKit, but there are additional devices for other platforms.


If your goal is to find someone lying in bed, sitting on the couch, or sitting in a specific chair, including an office chair, you can often do this very effectively with a pressure mat. There are a whole bunch of DIY project reports on how to make them smarter in places like Instructables, but the basic approach is always the same.

A) buy a pressure mat. These come in all different sizes, from a few dollars for one that may measure an ounce or two to around $75 for someone who knows when a car is parked on them. It’s basically two pieces of rubber or fabric that close a circuit when they come together and are calibrated so that a specific weight exerts enough pressure on the mat for the two pieces to touch.

You find them in all kinds of crazy places. At the maritime supply station where they serve as a “bell” for a barge. (When someone steps on the mat, a circuit is completed and a chime may sound). In medical supply houses where they are used to monitor patients getting up in the middle of the night. Robotics provides businesses where they are used for fun projects like knowing when your drone has parked.

This part itself has no radio inside. It’s just the piece of carpet.

B) Now wire this pressure mat to a smart open/close sensor so that when the pressure mat circuit closes, the smart sensor signals the change in state. Aqara sensors are popular for these because they’re cheap, but you can do this with most HomeKit-enabled sensors, including Eve. (To work with HomeKit, the aqara sensor also requires an Aqara hub.) The exact details will depend on the sensor model, but you should be able to find this information

Here’s just one example, but again, lots of people have done this with lots of different devices. It’s just a way to add a radio notification to a pressure mat.


So if the goal of your occupancy use case is to know that someone is sitting or lying somewhere, a pressure mat can work well.

If you just want to buy one that works out of the box and don’t mess around with the wiring and disassemble the sensor, you can use the Withings sleep mat, connect it via IFTTT to trigger an inexpensive Meross smart plug and use the Meross plug to bring state change in HomeKit. It would cost a lot more, and it’s cloud dependent due to the IFTTT step, but it’s pretty easy to set up and works well for a bed or couch. Too big for a chair, though.



There is currently an incredible thermal sensor that performs occupancy exactly the way most people who think of home automation occupancy want it to work. It’s almost instantaneous, it can tell when there are two people in a room and one share, it even works with HomeKit although not certified. It’s just very very expensive for a very small company. People who have it seem to like it, but you’re talking about a $200 cost per door. Maybe $120 each if you do at least five rooms. Oh, and it’s plugged in, no battery.


It works locally. I’m not 100% sure, but I think it would still work even if the company went bankrupt, at least via HomeKit. I would check with them to be sure though.

I can’t afford it myself, but as a wheelchair user it’s definitely on my ‘when I win the lottery’ wish list. The engineering of this thing is amazing.

So those are two “current” possibilities, depending on the exact use case.

I know a lot of people who use a variation of a pressure mat, and if you go DIY it can be quite inexpensive. You don’t have to carry anything with you, and it’s able to recognize true occupancy because it’s based on the physical weight of something in the room. A person sitting in a chair or lying on the bed, but maybe even a cup of coffee on a particular coaster.

I don’t personally know anyone who uses the hiome thermal sensor system, but all of the hands-on reviews have been good. It’s just very expensive.


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