Hold on, Revit doesn't do leaders from the correct location!!!
Well you're right it doesn't, and it also won't let you add a leader arrowhead to space tags. A big oversight by AutoDesk.
1. Create a blank annotation family and save it as Leader. 2. Create a family type for each leader arrowhead you want (i.e. Arrow, Dot). 3. Load it into your project and set the leader arrowhead for each type in the respective Type Properties box. 4. Place your new annotation and add as many leaders as you would like. Starting and ending from anywhere.
I have not found a way to align this leader to anything. So it is really more of a drafting mark then the fancy parametric, associated, live annotations we are used to in Revit. Also, if you place one of these without any leaders it can be hard to find (it is invisible after all). So you just have to be careful with these so you don't have a ton of blank annotations floating around.