1. A sensor comprising a quartz crystal having a first face and a second face, said first face comprising a prong, said prong being metallized to said first face of said crystal, wherein said prong has a frequency of vibration that substantially matches at least one frequency of vibration of said crystal and said sensor is adapted to track movements of an object in a medium other than vacuum by correlating a shift in a natural frequency of vibration of said crystal to an event of significance.