An electronic medical device is disclosed here. An exemplary embodiment of the medical device includes a printed circuit board assembly, a protective inner shell surrounding at least a portion of the printed circuit board assembly, and an outer shell surrounding at least a portion of the protective inner shell. The printed circuit board assembly has a printed circuit board, electronic components mounted to the printed circuit board, a battery mounted to the printed circuit board, and an interface compatible with a physiological characteristic sensor component. The protective inner shell is formed by overmolding the printed circuit board assembly with a first material having low pressure and low temperature molding properties. The outer shell is formed by overmolding the protective inner shell with a second material that is different than the first material.