Ringu turns a QR code into a doorbell

Field notes

Ringu assigns each installation a 22-character code that becomes a printable QR marker for a gate or door. Visitors scan it with an ordinary camera, press a button in the resulting web page, and trigger an alarm-style alert on the household phone. The page says the visitor receives confirmation after the alert is acknowledged, while repeated presses are throttled to one notice every 30 seconds. Recent rings remain visible in the app with their times. The Android package is currently distributed outside the Play Store.