[Plusea] made her own touchpad using some anti-static gloves and an Arduino. This proof of concept is fairly small, but the system could be scaled quite large if you could find the fabric. She cut apart the anti-static glove, mounted it and wired it to the Arduino. A special piece is made to fit over the finger that is also wired to the Arduino. The location of where she touches is determined by the resistance between the finger and each corner. Watch the video on the instructable to see how it measures.
She mentions that there are a few different ways to build it, some which would not require anything on your finger, but would use another piece mounted behind the touchpad. The method she is currently using though, would allow for the fabrick to be any size or shape, even molded around something.