what you are asking for is available in ISBoxer, and it can do just that, clickin in regions on one screen passes the clicks to another.

However healing isnt that hard to macro for 5 mans. Just make a few macros that heal your main, either by focus if you use that system, or by character name, and make a few macros that target off of the tanks's target, meaning whoever has aggro. I heal with a holy priest and don't have to do much other than pre cast some hots before the fight, and i have a healing macro thats on the same button as my dps buttons, that is mostly commas. its something like this

/castsequence [target=focustargettarget] renew,,,,,,,,,,,prayer of mending,,,,,,,,,,,,,,,,flash heal,,,,,,,,,,,,,,renew,,,,,,,,,,,,greater heal

and thats my mindless "heal whoever has aggro" button, and on top of that, I have keybinded a few other heals directly to my tank, and then there's AoE heals for the rest of the group.

You will get the hang of it. And as you get geared, youll find that you dont need much healing at all. lately ive been swapping action bars on my priest to spam smite, as her heals were just a waste of mana...