armor::onTrigger is used for several basic control functions. Its arguments are as follows:
armor::onTrigger(%this, %obj, %slot, %val)
%this is the datablock of %obj, the player object calling the function. %slot is the slot (0 for primary fire, 1 for secondary fire (there's no default keybind for this), 2 for jump, and 3 for crouch). %val is whether the button is being pressed or released (0 for released, 1 for pressed).
I don't know of anything you could use for starting/stopping walking, though.
