If I wanted random surfaces to become touch surfaces... I'd probably just use a discrete camera and some motion detection.  You could use downward-facing camera tucked into crown molding to define an area of wall as a light switch or something.  Maybe a dimmer switch.

But if you're going to do that it'd be a hell of a lot better to have a location and context-sensitive smart watch app.  Why get up to go over to the light when your watch knows what room your in and offers you the appropriate controls?

Or, going back to the camera idea, you could have the system watch the whole room and use gesture control.  It might be fun to wire your home with two-way sound and be able to trigger a VOIP system with a finger-and-pinky gesture beside your head.