My wife and I are moving with our two little boys into a two story house I had this idea. What if there was a trigger on the baby gate that we are going to put at the top of the stairs to let us know if it is closed.
I have figured out a way I think I could do it using something like a raspberry pi and having it email a notification when the gate it opened but I thought I would send you the challenge because you could make it better and add more features.
I am thinking some features could be time periods. So it will only alert you if the gate is open during certain parts of the day like night time when everyone is sleeping at it should be closed.
Also maybe kind of like a tilt (see how I am using pin ball terms for you) feature so if one of the boys wake up and tries to climb over the gate or shake it open.
I haven't looked around to see if there is already something like this available but I think a lot of parents would appreciate something like this.