LOL You're a control freak!
I never gave my kids any keys. They entered through the garage with a standard wireless keypad, into the mudroom with a mechanical, autolocking, programmable combo lock (was brutally expensive years ago). The only danger in a storm or bad weather was a power failure to enter the garage. We had a garage door key hidden under the deck for them...may be still there??...LOL
WIth the combo locks the first thing their friends do is to try to beat them and spy when they press the code in. The kids also like to show off to their friends and show them. First hint of that and the combos were changed each time. They grow out of that.
The electronic Schlage ones I have in this new house take many combos. Guest passwords are easily installed and dismissed again. It is nice to allow deliveries into the garage but not into the house although most of my tools are there.
A webcam with special software may be your answer. Some will "ring" the other end when motion is detected but a monthly service fee is always the drawback on that one.
The lighting things was mostly for stairs lights for guests staying over and late or night lights. If you get up to pee the light turns on and the motion det. turns it off in 2 minutes. If it is dark outside CPU sends an off signal after about 30 seconds.
Another cool thing was a "somebody home" macro. If nobody was home that night (based on Mot Det and button sensing all over the house) and based on a partial random times sequences of lights went on and off starting upstairs and working there way down to the porch light and then back to bed again. This worked so well a few neighbours knowing I was away for a week or two had a meeting on our front lawn whether to call the cops when nobody would answer the door...LOL
I am looking forward into getting back into it but the co-gen inverter noise is a pest with this stuff. A better system is in order for sure.
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Since my immediate need is the door lock, I thought I'd use that as a starting place. If I can find a decent lockset that integrates with another home system, that might be the push I need toward a particular platform. I'm not afraid of homebrew stuff for non-mission critical elements either. That would actually make the whole process more fun. (I want to learn about arduino or similar platforms and thought using them for a home automation project might be a way to do it.)
You went quite a bit into motion detection for lighting. While that might be nice, I'm actually more interested in knowing who entered the house, and not that there's a person there. I have small kids that are just now getting big enough to start allowing them a little more freedom. I don't necessarily need to be there the moment the bus arrives, but it would be nice to know that they made it home. The low tech solution is they walk in the door and call me to say they're home, but there has to be an easy approach to this since I'm going to be changing the locks anyway. (Keys are not a good solution for these kids. One of them loses his glasses on the way to the bathroom. :-) )