Well, there's also the low-tech solution of having a doorbell that makes a ringing noise and then you get up and answer it. I suppose that doesn't work over the Internet, but I can't really figure out why I'd want to let anyone without a key into my house when I wasn't there. (But then I live a very simple life.)

(I often think I have far too little geekery in my life for a geek. I can't even close my blinds automatically. I can't even figure out how one might do that without replacing one's blinds, probably light bulbs, likely light-bulb holders too, and tying oneself to a mass of impossible-to-configure, half-proprietary nightmares that go obsolete in two years and leave you with blinds and lights you can't turn on at all. The only tempting thing about your setup to me is that it's got a lot of free software components which probably will not go immediately obsolete, and at least you found a doorbell that wasn't mandatorily tied to the cloud...)