Interesting. I just talked to a customer the other day about a light-sensing alarm. The idea is to trigger the alarm (which also sends a push notification) if the ambient illumination goes above a certain level during a specified period of time (say, during night). This is actually quite easy to do. So what you want is similar, but you want the gadget to sense the door / window opening and trigger an alarm (or even a action such as turning off AC / heat) when it happens. Right? What’s the technique to sense the door / window opening? I’ve seen home security systems using a magnet plus a reed switch (or hall effect sensor) to do so. Wondering if you prefer a different way.