RFID

Because we want the system to be able to recognize the amount of time a user spent on the system, we thought of using RFID tags, like these ones:

Since we want to check the amount of time a user spends in front of our product, the RFID tags can be checked in at the beginning, and at every station.  At the end, the amount stations tagged would calculate the weight of the vote.

These tags will stay with the person, and go with them from vote to vote.