This is $6 less than anywhere else (more if you count free shipping).
Brad's Deals Editor David,
This Monoprice Z-Wave Plus Door and Window Sensor drops from $25.69 to $14.99 with free shipping at Monoprice. This was the best price we found by $6. This detects when a door or window is opened and emits a sound. If it's connected to a Z-Wave (a wireless protocol supported by many brands) controller unit, it can send alerts to remote devices. Sales tax is charged in most states.