We will need to know what country you are in, as the device selection does vary. And whether you have a SmartThings/Aeotec hub or not. And those cases, the device selections will vary.
OK, that stuff out of the way, Aeotec has a Z wave multi sensor with an available “recessor” specifically so it can be put into the ceiling. It’s Z wave, so you definitely need a hub. And it does work well with smartthings. It’s also available in many different countries.
It’s not invisible, but most people think it looks like a smoke sensor.
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There are other options from other brands, but that should give you an idea.
Yet another option is a very new technology, mmWave sensors. These have a number of advantages over the traditional “passive infrared“ (PIR) “motion“ sensors. For one thing, PIR sensors are detecting small changes in heat that pass across the lens. So while they tend to be really good at noticing someone come into an area, Once all the heat is equalized, they may think there’s nobody there even if someone is still sitting on the sofa or at a desk. In contrast, MM wave sensors are great at detecting “very fine movement“ like a person breathing. So they are much much less likely to turn the lights off before you want them to.
Also, and Mwave sensors can detect through then plaster walls or through plain clear glass. While this does mean set up is more work than a traditional PIR sensor because usually you have to mark the edges of the room, where you want the sensor to detect, it does mean they’re easier to hide, because you may be able to put them in the ceiling, or even inside a basket. this is one of those trial and error things, but it’s an option with this technology that you do not have with PIR sensors like the one I already mentioned.
Because the MM wave sensors have to process so much data to work, they are almost all mains powered.
And many of them are Wi-Fi, and will not require a hub of any kind.
One of the biggest downsides is the cost: most of them will be in the $75-$100 range, as opposed to traditional PIR sensors, which are usually under $40 and maybe even less. So I don’t know if you’d be interested in those or not, but I did want to mention them.
The aqara fp2 is a popular model of MM wave sensor right now, available in many countries. The only integration with smartthings at the time of this writing is through an intermediary like Alexa routines, but both Aqara and Samsung have promised us better integration in the next few months. Meanwhile, there are a number of people using them already with an intermediary. (Including me). So that’s another option to consider.
Best mmWave Sensor to Use with ST? (human presence sensor/occupancy sensor)