Yes, but your detector creates more problems than it solves:
* pets set it off,
* it cannot differentiate between different objects in motion. So several people could be moving at the same time and it would only trigger as one event,
* it cannot detect people who are present but motionless (eg watching TV),
* it doesn't remember how many people are present in a room, so you could have 2 people watching TV then when 1 person leaves the detect would think the room is empty,
* it requires multiple detectors,
* detectors are generally visible, which some might find an eyesore (at least WiFi APs can be hidden a little more as fewer needed).
I'm not saying FIND is perfect either, but you have implied that your solution works just as well as FIND and stated that your solution is less complex; which is simply is not true. Your solution creates more problems than FIND and addressing them creates just as much complexity (as I detailed in my other post: https://news.ycombinator.com/item?id=11519159)
Motion detectors have a variety of usage, outdoor lighting, indoor room lighting, grocery store fridge lighting, etc. FIND is a bit more specialized because of the huge drawback of requiring each user to carry a specific device.
I can't use it at my work because we don't all have Android. I can't use it at home because my wife uses in iPhone. Cool idea but limited use compared to motion detectors.
Indeed, but that was never in dispute. FIND was never pitched to replace motion detection sensors to begin with. The argument was whether motion detectors are comparable to FIND for the specific specialised problem that FIND addresses to solve; not whether FIND can replace all the generalised purposes that motion detection is utilised.
My point was always that the two technologies aren't necessarily interchangeable and in an indirect way you're just saying the same thing with your counterargument.
The original comment was about turning lights on and off. You implied FIND is better than motion detectors at this ("your solution creates more problems than FIND..."). In most cases this is false, due to the negatives I outlined above.
I think the confusion here is there's two different use cases for turning lights on and off.
I have acknowledged in another post that motion detectors are advantageous if you're dealing with strangers and/or situations where there's lots of movement and/or lights that can be automatically timed out. eg public spaces halls, public restrooms, security lights, etc. But I don't think it's fair to lump these in the same category as "home automation".
Home automation is a little more of a complex problem as you need the lights in the room to not only turn on when someone enters, but also turn off when they leave. Motion detectors can spot someone moving in a room but they're not to great at detecting when people have left since it's the same sensor that would be triggered. They're also not great at detecting if people have entered a room and are still in the room if those people have stopped moving (eg they are watching TV) - since those people aren't triggering the motion detection. And lastly, motion detection isn't great at detecting the number of people in a room - which matters if you don't want the lights to turn off when someone leaves the room but other people are still in there and watching TV.
Motion detection solved some of the problems of home automation, but creates some problems as well. Which is why I said motion detection is just too simplistic of a solution for home automation despite it being a great solution for other types of automating lighting.
Granted you could place more sensors, network them up, and have a centralised unit logging movement. That would likely work. But then it quickly becomes as complex as the solutions we're trying to avoid.
However even if all these things were easily addressed, motion detection still has issues for me personally as I have two cats. This is the beauty of proper home automation systems: they give you the granularity to personalise things so pets don't set off the same triggers that people do. Or my two year old doesn't trigger the same automation that my wife and I do (eg unlocking the front door). This is where I think the future of home automation lies and is what really gets me excited.
So you're right that there is overlap between motion triggers lights and home automation; but the latter is intentionally a more complex problem by design.
I'm looking at building my own home automation, the PIR sensors are fairly heavy on power and in order to ping them fast enough I need a fairly large battery or hook up the sensor to electricity. If I can replace that with a device in my pocket it would be nice as I don't need extra sensors.
Ofcourse, the downside is if the device is not in my pocket the system has no way to know where I am and will keep the light on in the wrong room and keep me in the dark so it's not like it's a perfect solution.
There are PIR sensors that use no more than tens of microamps of power, and can send an interrupt signal to a microcontroller to wake it from deep sleep. An example is AMN41121 by Panasonic.
