This was a class exercise in Tangible Interfaces I did with Richard The and David Pitman

What if instead of using buttons and knobs for single use interactions, everything would just do what we wanted it to when we knocked on it? Knocking on your computer would open and awaken it, knocking on the elevator would call it, knocking on the coffee machine would make you coffee. What if your bike recognised it was you knocking, and locked and unlocked for you? It would be great!