This is just a simple mobile I put together awhile back for testing dps to balance things like weapons, spells, pets, ect.
The Dps Golem (yeah I know it's an elemental ) will display a simple overhead message after ~10 seconds of taking damage. This message is calculated from all damage taken from all sources over the last ~10 seconds and is displayed as dps. It requires steady damage during this time to work though as it only calculates/displays when hits change (e.g. hitting it once and stopping won't display a message after ~10 seconds).
Warning: This was made for testing purposes and probably should be the case for it's use. Players and pets will still gain skills from attacking/casting on it and that will probably turn it into a skill macro'ing mobile .