Google failed to help me with this one. Probably because this might be called something else.
A few months a I was at local gathering and someone who seemed to really know what he was talking about, explained to me that capacitance could work two ways. One way to sense obviously and another provide feedback through a very subtle shock or something. One of the guys demonstrated the effect with his macbook air plugged in and touch a specific spot on the uni-body.
Said it was used for silent triggers and things of the like.
I'm interested in using this type of feedback in place of pager motors for my project. Anybody know of any resources to get started?