A vital-signs patch for a patient monitoring system is disclosed. The patch consists of a housing that is configured to be worn on the skin of a patient. The housing contains a radio, one or more sensor interfaces, a processor, and a battery. The processor can selectably turn portions of the processor off and on and selectably turn power off and on to at least a portion of the sensor interfaces and radio. The processor includes a timer that, each time the timer times out, will turn all the parts of the processor on and start a new timing period. When the processor receives a signal, the processor will turn off power to at least a portion of the processor and at least a portion of the sensor interfaces.