Window sensors cost $10-40 each and cover the entry point burglars use 23% of the time (FBI UCR data). Magnetic contact sensors ($10-20) detect when a window opens. Glass-break sensors ($25-40) detect shattered glass from 15-25 feet. Vibration sensors ($20-30) catch both. We ranked 5 sensors by detection range, false alarm rate, and battery life. Abode’s mini door/window sensor ($15) is the best value — works with Z-Wave, HomeKit, and CUE automations. SimpliSafe and Ring sensors cost $15-25 but lack Z-Wave and HomeKit. Installation takes 5 minutes with adhesive backing.

