A small resistive touch screen would do, but I have yet find any such product on the market. It need only be about 1 inch square, and respond to simple touch/no touch. I am considering making the part myself, but I am not in the habit if reinventing the wheel. Is there an existing product that might work here? Or perhaps there is another method of touch sensor that can be implimented.
An optical approach we suggested, such as an infrared emmitter/detector, but ambient light levels, and packaging contraints have ruled that out.