Detecting, Locating Objects on Tablet PCs, mimicking touchpo

Looking for a neat solution for conducting a charge from a user to a computing surface via inanimate object (most likely plastic or wood). Plus the development of a corresponding proof of concept application on iPad in either Unity 3D or Objective C. View example [login to view URL] Solution must be non-toxic and non-powered. Not seeking new methods of manufacture, simply a tagging system for existing objects only. Thanks for your bid.