Description of problem:
  Comment does not match code.  I don't think that does what you think that 
does.
  
Actual results:
 The shutdown will be run only if the ps includes "grep" in the return 
results.

Expected results:
  The shutdown will be run only if gnome-power-manager isn't in the ps list.

Additional info:
  I think you meant
action=/bin/ps 
awwux | /bin/grep -q '[g]nome-power-manager'  || /sbin/shutdown -h now