Intelligent data network with power management capabilities

A method for implementing two-way wireless communication between at least first and second ambulatory devices, comprising steps of:

• (a) during finite time periods following reception by the second device of respective first messages from the first device, when the second device needs to communicate with the first device, powering on a transmitter included in the second device and using the transmitter included in the second device to transmit second messages to the first device;
• and
• (b) after each of the finite time periods following reception by the second device of respective first messages from the first device, powering down the transmitter included in the second device and ceasing to use the transmitter included in the second device to transmit second messages to the first device until after the second device receives another first message from the first device;
• wherein the first and second ambulatory devices are each being carried by a person and powered exclusively by a battery when the steps (a) and (b) are performed.

A second, ambulatory device capable of engaging in two-way communication with at least a first device, comprising:

• second circuitry configured to render the second device operable as at least one of a wristwatch, a cellular telephone, a personal data assistant, and a portable music device;
• a second transmitter;
• a second receiver;
• and
• at least one second controller coupled to the second transmitter and the second receiver, the at least one second controller being configured to power on the second transmitter to transmit second messages to the first device during finite time periods following reception by the second receiver of respective first messages from the first device, and being further configured to power down the second transmitter after transmission of each of the second messages from the second device to the first device.