A vital-signs device in a patient monitoring system is disclosed. The patch includes a housing configured to be attached to the skin of a patient. The housing contain monitoring circuitry configured to acquire and store measurements of vital signs of the patient, a wireless transmitter configured to transmit signals to another device, a wireless receiver configured to receive signals from the other device; and a processor operably connected to the monitoring circuitry, transmitter, and receiver. Upon receipt of an upload signal from the other device, the processor is configured to send a message to the other device via the transmitter. The message packet structure includes a data payload of variable size, a header containing transmit and route information and data payload length, and a data integrity check value.