A monitor provides a wireless signal with respective pulses, based on a heartbeat, repetitive physical movement, or other repetitive bodily action of a user. The pulses include longer duration pulses whose duration identifies the monitor, and distinguishes it from other monitors which may provide crosstalk interference. The longer duration pulses are interspersed among short duration pulses to reduce power consumption. The pulses are transmitted in successive cycles, where the number of the longer duration pulses is set adaptively in each cycle based on a detected rate, or rate of change, of respective instances of the bodily action. A receiver unit processes the signal to determine a rate of the bodily action and provide a corresponding output. The receiver unit can synchronize with two or more consecutive longer duration pulses. The pulse duration can be fixed or determined dynamically, e.g., non-deterministically.