The varied capabilities of each small sensor are what make Notion unusual. A single pod, about the size of a stereo’s volume knob, can measure a change in room temperature, the acceleration of an opening door, or the illumination from a lightbulb left on. Sensors have a Piezoelectric transducer, which measures frequency—Notion's example is that you can stick it to a propane tank and know how much volume it has left. Photo 2 of 5 in These Tiny Hubs Will Make Your Home Smart and Safe by Alexander George

These Tiny Hubs Will Make Your Home Smart and Safe

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The varied capabilities of each small sensor are what make Notion unusual. A single pod, about the size of a stereo’s volume knob, can measure a change in room temperature, the acceleration of an opening door, or the illumination from a lightbulb left on. Sensors have a Piezoelectric transducer, which measures frequency—Notion's example is that you can stick it to a propane tank and know how much volume it has left.