Series 1 sleep mode using line pass

I am starting out using the series 1 XBEE module/radios. I want to configure a sensor using line pass
to send a switch status on switch change. I have this part working ok.
I am looking for the best method to reduce battery usage to the lowest I can.
In examining the various sleep modes it seems that mode 4 is the best. I don’t understand
exactly what happens when the module wakes from sleep mode. Does it sample the pin condition
and then send that condition to the base?
What would be the best scenario for me would be to have the sensor, no micro just the module,
to wake up send the status and then go back to the sleep mode until the wake up next.

The Digi manual ( 90000982_G, 3/13/2013) on page 32, defines the sleep mode (SO) options.
It defines the parameter ranges as 0-4. But, there are only two bits described in the manual.
Is this a typo or is there a missing additional bit not listed?
In the SO explanation, bit 0 indicates that the module “will poll for data on waking”.
Does that mean that it is polling for the local, sensor pin change or it means that it is checking
for data from another module?

How would I set up the sensor module to transmit the status and then go to sleep in the shortest
amount of time?

I would appreciate any advise on getting straight on these issues.

I plan on operating the sensor module directly from batteries. The ‘base’ would be powered by a power supply (walwart) and proper regulation for the 3.3 VDC requirement.