Abstract: An instrument and method for non-invasively deriving at least one biometric datum of a living vertebrate. A sensor positioned against the vertebrate measures vibrations within its body. The sensor provides the samples to the instrument as at least one time-stamped stream that correspond to one or more linear and/or rotational acceleration measurement axes. The instrument organizes the samples into windowed streams, separates them into a first set of streams corresponding to physical events of the vertebrate associated with cardiovascular activity and a second set of streams corresponding to physical events of the vertebrate associated with respiration. A datum can be extracted from the first set by autocorrelating it with a time-delayed version thereof to identify at least one characteristic peak of the vertebrate's cardiac cycle. A datum can be extracted from the second set by determining a characteristic frequency of respiration of the vertebrate.