Buttons and Sliders were always meant to be able to set their targets and their actions. Due to a very persistant bug the target setting was alway hidden from view.
In fixing that I realized that what was wanted was a way to pick anything visible on the screen as a target. So I created a James Bond gunsight cursor and modified the embed code to allow target sighting anywhere on the screen.
When no one seemed to understand why this was desirable I created a play-with-me to show the power of this.
Right now target sighting only works for Sliders.