Abstract: Disclosed is a monitor apparatus which can be worn by a patient and will provide an indication of activity levels over a number of subsequent time periods. A transducer which is energized by the ambulatory subject's movement, provides an activity pulse into a temporary memory. At the end of a standard timing interval, for example fifteen (15) minutes, a digital code word representative of the total number of activity pulses in that standard timing interval is fed into a solid state memory. The temporary memory is then reset and counts the activity pulses over the next standard timing interval. In this manner, activity levels for any number of sequential time intervals can be recorded without hindering the patient's movement. A contol logic circuit, which is externally triggered, causes the permanent memory to sequentially readout the activity levels of subsequent standard timing intervals for use in studying the activity levels of ambulatory subjects.