Because of this I'm not comfortable calling it done, but since it will need to be re-coded entirely, I thought I'd at least put this out there for anyone who wants to try it. It works great on boobs from the front though.
Download Jiggle and Grow (Update: Please download the updated Jiggle and Grow Script instead)
Drop that file into your After Effects Script folder (C:/Programs/Adobe/After Effects version/Scripts/).
Then you can run it in AE: File -> Scripts -> Jiggle and Grow.
Mask off the boob. Run the script. It will duplicate the mask for you.
Run the script again (this will be fixed in later versions). This time, adjust only the new mask to the desired size. Making sure that at least some of the anchor points stay put (usually the ones at the top).
When done, run the script one last time and it will add all the fun stuff.
All you need to do now is keyframe the reshape's percent and it will add jiggle in automatically.
I would consider this beta for people who are familiar with AE or at least in using my other script.
If anyone was really looking forward to this, I apologize, I will try and get the next version out soon. Because I can't use the reshape effect for this now, I'm left with using the puppet tool - which I have no experience working with. I can't use liquify, or run anything off of it, because liquify's displacement map is a custom variable (like Reshape's correspondence points) so nothing can touch them except the user.