Hi Guys,
These links show examples of on/off circuitry commonly used in calculators,
mobile phones, and other battery-operated devices.
The p-channel MOSFET serves as an electronic power switch.
They look ideal for pic based circuits, so I gave the first example
a shot.

Description:
http://www.reed-electronics.com/ednm...=0&rme=0&cfd=1
Figure 1:
http://www.reed-electronics.com/ednm...es/54571f1.pdf
Figure 2:
http://www.reed-electronics.com/ednm...es/54571f2.pdf

The 5K1 resistor in series with the switch S1 in Figure1
only appears to short the battery.
I have constructed the circuit on a small PCB, and had no luck.
I tried connecting another 5K1 resistor between Q1 gate, and
the switch end of the other 5K1 resistor because I thought it
might have been left out.

I found that the P Channel MOSFET was powering the 7805 reg
no matter what I did to the gate pin. It even provides power when the gate pin is disconnected.

Any suggestions?... I don't have any experience with MOSFETs
Art.