RFID Gesture Generating Robot

I am interested in the human reaction to physical motion, particularly the characteristics of motion that make something appear elegant as it moves. In addition, I am fascinated by how one can encourage empathy with a machine by the way it moves. I am convinced that a moving, tangible object has a different impact on people to a 2D image displayed on a screen.
I propose a robot made of two stepper motors mounted so that one rotates in a horizontal plane and one in a vertical plane. They move a wand-like appendage in space, much like a orchestra conductor's baton. An RFID reader mounted on the window glass reads people's Oystercards and generates a pattern of motion from the tag number and thus generates a gesture that is unique (and repeatable) associated with that card. It is an elegant, sweeping kind of motion, changing the path and speed according to the tag number. When a tag hasn't been read for a while, the robot will drift around, giving the impression of "looking" for people. I would not want it to be ever completely static, as that is one cue we use to recognise machine motion rather than natural motion (animals are rarely 100% still).
Gesture generation algorithm
Mifare cards (including Oystercards) store a tag number as 4 bytes (allowing 4,294,967,295 different tag numbers). The algorithm splits the bytes into nibbles (4 bits), giving a array of eight values each ranging from 1 to 16. Sixteen (arbitrary) points in space, arranged around the periphery of the robot's workspace, are assigned these values. When a card is read, the robot starts moving towards the point representing the first nibble in its tag number. Before it can get there, the point associated with the next nibble starts attracting the robot. Again, before it gets there, the following nibble attracts it. This continues until all eight points are processed. The motion is smoothed so that the robot moves in sweeping curves. Thus, each card will generate a pattern unique to that card, but one that is the same every time the card is read. The gesture generated “belongs” to that card user.
I have written a simulation program that generates gestures from Oystercard tag numbers. When it runs, it is clear that the robot is “trying” to get to a destination, but is always prevented from doing so. This triggers and empathic response from an observer and one “feels sorry” for it. An association between being thwarted from ones attempts to travel to a destination and the use of Oystercards is encouraged.
The base of the robot will be made sufficiently heavy to prevent it toppling over.
For safety reasons, the display area would have to be enclosed to prevent access to the arm while it is moving. A safety interlock switch would be mounted on the access door to disable power when it is opened. Only authorised people would be allowed access to the machine. It is designed to be operated continuously with no maintenance required.