Abstract: A wireless package-mounted sensor system to detect an opening of a package. The system may measure, at each of a plurality of sensors mounted to a plurality of different respective surfaces of the package, an orientation of the surface onto which the sensor is mounted. At least one of the sensors may be mounted to an adjustable surface intended to open the package. An open package test may be executed comprising determining a relative orientation between the sensor mounted to the adjustable surface and another of the plurality of sensors mounted to another of the plurality of different respective surfaces, and determining the package is open if the relative orientation changes from a threshold range indicating a closed state to a threshold range indicating an open state. An indication of the determination that the package is open may be wirelessly transmitting.