Nice idea for a project.
What would you read the data on? How would you know if a person walked in a room or out? I Think it would take two sensors working together, so the logger would know what direction someone was going. Could be done, but on what. Could use a micro-controller and a LCD or even use 7 segments for the counter. Two ir detectors set at angles could track the movement.
What part do you need help with rpbz?
gogo