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).
* 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.