A heart beat rate monitor is provided with memory means for storing upper and lower limits of a range of heart beat rates. The limits are transmitted to and stored in the memory from an external source. The monitor wearer's heart beat is sensed and whenever the sensed beat rate is outside the range defined by the limits an out-of-range indication is provided to the wearer. The memory means are powered so as not to be affected by the depletion of the main battery which is the primary source of power for the monitor circuitry. In some embodiments, the limits received from the external unit are transmitted thereto for verification purposes. In some embodiments the actual sensed heart beat rate and/or the stored limits are displayable to the wearer upon request.