I first made Hue-topia and LIFXstyle some years ago after becoming very paranoid (justifiably) about intruders.
At the time, no sensors existed for the system (at least as consumer products - Philips went with the zigbee network system, which in theory means that there were other third-party products that would work). I experimented with sound and motion detection using EyeSpy cameras, which worked. The security aspects of Hue-topia and LIFXstyle were the reason for the dragon icon (someone asked this question recently).
Both Philips and LIFX added products to their range - more bulbs, switches, sensors. I had to purchase any products I wanted to support, which would have cost more than the revenue from the apps. For this reason I stuck to supporting only the lights in my apps.
This is the reason that I'm very late to the party with the motion sensor, and I have to be honest, wanting an outside temperature reading is the main reason I went for one.
Yes, each Philips motion sensor, despite the name, also contains a thermometer and possibly daylight sensor (though I've a feeling this may be calculated by the bridge and not a sensor, but I can't go back in time and check whether this pre-existed my first motion sensor).
Anyhow. Thanks to Philips' open API and REST interface, it's very simple to read these sensor values. As you can see in the first screenshot I've added a little functionality to Hue-topia (in my development version thus far). I can now see the outside temperature* from the status bar of any of my computers/laptops.
I have to say that adding my first motion sensor to my network was a breeze. A magnetic mount makes it very easy to put up (and take down to change the battery). It's a tiny thing, which makes it discreet. It's battery-powered which was important to me. The last thing you need is another thing to plug into a socket. Having to route wires is a pain and restricts where you can place it. When I pulled the tab to connect the battery it started to flash, which seemed to indicate that it was searching. I chose 'Discover' in Hue-topia and the flashing stopped. It was then working on the network without me even having to walk to the bridge and press a button. I obviously have yet to discover how long the batteries (2xAAA I think) last.
Traditionally and personally I've leaned towards the LIFX system; the bulbs were brighter and did more colours*. I have to say that, many years on and many bulbs later, I own more broken LIFX bulbs than Hue bulbs (3:1). As well as this apparent better reliability, the Hue bridge is a good thing. Yes, it's an extra product to buy and give space (and a power socket) to. LIFX use 'bridgeless' as a selling point. But the Hue bridge does have a lot of functionality and is always on, more reliable and maintenance-free than my 'always on' mac. After moving house, the Hue bulbs have been easier to get working again than my LIFX bulbs and strips.
In short I'm warming to the Hue system and I'm liking the motion sensors a lot. My rule for switching the porch light on when motion is detected is working really well*. Its sensitivity seems just right, it seems to talk to the bridge reliably even though they are at opposite ends of the house and the sensor is outside (I seem to remember that the hue/zigbee system is a mesh, so the bulbs themselves may be serving as relays).
At this point I'm not sure how much of the 'rule' functionality I'm going to build into Hue-topia. Philips seem to have the 'formula' system sewn up into their mobile app. I've been using the built-in debug tool to add and edit my own rules (because I don't personally like cloud-based systems). Once they're set up, they're set up and it'll probably be only groups and scenes that I need to edit, so I suspect that building a 'rule builder' into HT would be a lot of work which would be of interest to very few people. Tell me if I'm wrong.
I may well release a little update that puts any temperatures detected into the status bar menu.
* I have read that this may be a degree or two out (I don't have a reliable thermometer here to calibrate mine) but it's a very simple matter to adjust this in software. I'll probably add a box in Preferences so that the user can enter "-1.2" or whatever
*I think some of the 'friends of hue' range did the full range of colours, but in the early days, the domestic-style Hue bulbs had a limited colour space. Green was weak and blue almost non-existent. I haven't tried more recently-produced bulbs. To be objective, I probably only sweep the colour range when showing off to friends and family. Other than Halloween parties or effects lighting, I can't see a use for a strong green or strong blue. In normal use I find that I like to use the Hue colour bulbs in 'white' mode, which gives you a spectrum from cold to very warm. That's all you really need in a domestic setting.
*switching off after a period of being on is not. I suspect that this may be because the porch light illuminates an area that can be seen by the sensor (which is part of the point) and so switching it off may be triggering it to come on again. I need to experiment more with this.