Thanks for all your input guys, I haven't expected such feedback in so short time. Of course, we don't need to hold religiously to monitoring camera activity - it was just me thinking loudly, if there are better methods available (like in magick777 analysis), lets use them.

Question here - monitoring things via inotify all the time (as opposed to just after camera activity) won't cause dramatic increase of power usage during idle? Sadly, I have no clue about monitoring such things at filesystem level, so my question ma be dumb - I just wonder if it require us to actively monitor something (which, while neglible during heavy usage, would much reduce standby time), or it works by some notification magick, that doesn't consume anything 'till trigger happens.

Again, thanks a lot for super-positive response!