This is one of the coolest add-ons… nah not really, It’s still a great add-on and it helps speeding up your rigging workflow quite a lot.
The way it works is simple.
First you have to select your geometry that has the shape keys and then you select the bone (in pose mode) that you want to connect to the shape key, go to the specials menu and down at the bottom there is the “ShapeKey Driver Constraint” you will get a menu to adjust the values (the same way you’d do it in a driver, choose the axis and type of transform the controller will move in, space type, and the range of movement) and you’re set.
Now, to make it easier, Andreas Esau made it so that if you can move the bone first (in pose mode) to the position where the the shapekey should be at 1 (full influence), and then when you activate the “ShapeKey Driver Constraint” the addon will have already figured out what you want to do so you can just click OK.
Also if you just started rigging, and you’re planning to do your shapekeys later, you can also connect the control bones to an empty shapekey by selecting “create new shapekey”
And really that’s all there is to it, super easy super simple, and we love that!
So don’t waste any more time connecting your drivers by hand, and go Download it from GitHub
If you wanna contact the author he’s here: https://twitter.com/ndee85
Happy Driving Shape Keys!