Last spring, I walked into my daughter's room on a mild afternoon and found the window wide open while the central air ran full tilt, cooling the great outdoors. She'd cracked it that morning and forgotten. The AC had no clue, so it kept running against an open screen for who knows how long. Most of my windows already had sensor-triggered automations wired up for the alarm and the lights, and it occurred to me that the same hardware could fix this, too.