don't think moving the mouse would work,
i mean when i afk, i came back and move the mouse to check guild statue, didn't clear my afk status.

you can find a afk mod in the net, maybe modified from bg running route type, let your toon run wild.
but the risk of hack are just too high.

well, i once paid my 3years old brother with chocolat sit there, let him face roll, kill randum low level mob.
i unplug usb mouse, just incase he get curious, starting to clear all my bag item.
can't do that anymore. he smarter that that now.

anyway, just a meta achievement, i pretty much ignore it.