Meet the Tripper: a smart sensor that lets you find out when your doors or windows are opened or closed. It allows you to keep tabs on every door and window in your house from your iOS/Android or Android Wear devices. You can use it to monitor closets, cabinets, and other places in your home. When the status of any door or window changes, you get notified.
Tripper connects to other smart home products to trigger certain actions. For instance, it can turn the lights on when you open a door. The device works with the Wink app but does require a smart hub. The battery life lasts up to 2 years. You can get a Tripper for $40.