This site contains affiliate links for which we may be compensated.
SimpliSafe Entry Sensor$14.99
Easy to install on every type of door or window. The magnet goes on the door or window, and the sensor goes on the frame (or vice versa). Magnet can be placed up to 2 inches from the sensor, so sensors fit on all types of doors and windows.
SimpliSafe sensors come with the battery pre-installed and adhesive tape pre-applied, making set-up a snap.