Meet the Tripper: a smart device that helps you monitor your doors or windows from anywhere. The device provides you with an alert when a connected door or window is opened. It requires a smart hub to work. It is compatible with iOS, Android, and Android Wear devices. The battery lasts up to 1 year.
Smart door/window sensors like this not only keep you notified when there is any intrusion, they also let you automate things around your home. Sets you back $40.