It allows you to set up sliders for any attributes, but lets you stay in whatever tool your using.

So say your painting weights on an arm, but you dont want to keep having to exit the tool, grab the ik handle, move it about, see it still needs work, select the mesh, select the paint tool and start painting again.
So what you can do is set up a slider for the ik handles y translation for instance, which lets you paint and move the ikhandle without having to go through the above steps. kinda hard to explain... i did do a tutorial vid that showed how this works a while back, but cant remember what thread it was in. anyway - best thing is to download it, and play about - it'll change the way you think about smooth binding ... i promise