A mouthguard (MG) controller with a wireless data transmitter was developed for unconstrained control of external devices. The MG controller was composed of three pairs of a pressure sensor and a Bluetooth low energy (BLE) wireless data logger for the upper and lower jaws. The pressure sensors and the BLE data loggers were sandwiched by two dental MG materials so that they were not exposed in the oral environment. Pressure applied to the sensor was measured as a resistance change, and an algorithm that exploited the sensor output to regulate the control of an external device, such as a smart device, was developed. The pressure sensor encapsulated in the MG material showed a dynamic range of 1.7–29 N. In an experiment using a jaw phantom, the response time to applied occlusal pressure was 0.18 s. Finally, the use of the measured pressure to manipulate a pointer in a smart device application was demonstrated. The results indicate that the developed MG controller enables the manipulation of devices in one's vicinity via occlusion.