Patent ID: 7937121

Claim:
A method for implementing wireless two-way communication between at least first and second ambulatory devices, comprising steps of: (a) during finite time periods following transmission of respective first messages from the first device to the second device, powering on a receiver included in the first device to enable the first device to listen for second messages transmitted from the second device to the first device; and (b) after each of the finite time periods following the transmission of the respective first messages from the first device to the second device, powering down the receiver included in the first device; (c) powering on a receiver included in the second device to listen for first messages from the first device; (d) transmitting at least some first messages from the first device to the second device that include information indicating when the first device expects to send at least one subsequent first message to the second device; and (e) powering down the receiver included in the second device during at least some time periods during which the second device does not expect to receive first messages from the first device; wherein the steps (a) and (b) are both performed while the first and second ambulatory devices are being carried by a person in locomotion on foot.