this was a mod, i can't for the life of me remember the name, but it was just as you describe, pressing one button over and over, i remember using it in molten core...but as of patch 2. whatever it was broke and noone ever made another one, best thing now a days is HealBot which lets you click a person's name in a little box to cast a certain heal, ie. left click is flash heal, right click is greater heal and mouse wheel is renew and so on.