Sequentially operated modules

A set for activating a payload in response to sensing a first physical phenomenon and for over-the-air wireless communication with a device, the set comprising:

• a first module that comprises a first enclosure, a second module that comprises a second enclosure, and a third module that comprises a third enclosure, wherein the modules are releaseably mechanically attachable with each other using protrusions, and cavities adapted to receive the protrusions in a frictional engagement;
• a sensor in one of the modules for producing an output signal responsive to the first physical phenomenon;
• a first payload in one of the modules for affecting second physical phenomenon;
• a wireless transmitter in one of the modules and an antenna for communicating using a wireless signal over a wireless network;
• a firmware and a processor in one of the modules for executing the firmware;
• a battery in one of the modules for powering the first payload and the wireless transmitter;
• and
• a switch in one of the modules connected between the battery and the first payload,
• wherein the processor is coupled for receiving the output signal from the sensor,
• wherein the processor is coupled for activating the first payload by switching power, using the switch, from the battery to the first payload, in response to the output signal, and
• wherein the first payload is activated by switching a battery power to the first payload.