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A characterization of the dynamic narrowband on- body to off-body area channel is presented based on realtime measurements of the time domain channel response at carrier frequencies near the 900 MHz and 2400 MHz Industrial, Scientific and Medical (ISM) bands. A statistical characterization is presented of received signal amplitude when the subject's body is standing and walking, transmitted from the body to a receiver, Rx, off the body, with various orientations of the subject's body with respect to the receiver, and various distances from the receiver. Two locations of the transmitter, Tx, on the human body are considered. The Lognormal distribution provides a good fitting model with and without movement. Further, the stability is characterized based on a measure of channel response variance, which is called here the channel variation factor and can characterize the channel coherence time. The on-body to off-body area channel is determined to be generally stable over a period of 25 ms, but the amount of stability is found to be dependent both on movement, Tx location on-body, and carrier frequency.