This is going to confuse the hell out of people who buy it second hand in 10 years time, especially if the maps go out of date.
And some cams emit infareds so there are many means to detect them.
The detector would have to catch "Scatter" from it from cars going through it or whatever. Which, IR is emitted from many sources, so it couldn't be used as a reliable way to detect it.
Also, a lot of the triggers are by video cameras. If you have ever setup any basic home security system(Like Q-See), you can choose areas as "Triggers" for recording. The operators of the cameras basically draw out areas that act as trigger zones. See this as something of an example: http://rhythmtraffic.com/wp-content/uploads/2012/10/WebUI.jp...