A medical device includes a sensor interface for measuring one or more physiological signals of the patient； at least one motion detector for detecting movement of the device； a processor coupled to the sensor interface and the at least one motion detector； and a memory communicatively coupled to the processor and comprising instructions that cause the processor to receive movement information comprising at least acceleration information and heading information from the at least one motion detector； detect movement of the medical device from the movement information, wherein the movement of the medical device comprises a distance traveled by the medical device and a direction traveled by the medical device； and estimate a current location of the medical device relative to a previous location of the medical device using dead reckoning based at least in part on the distance and direction traveled by the medical device.
