Movement of people

Hi, I have to count the number of people and survey the movement of everybody in a room. For example: if in my room there were 100 people I need data of position of everybody. How can I do this?is there a way to do it? thank you!

You can either put a matrix of pressure sensors on the floor and use that to determine where feet are OR you could use a bunch of overhead cameras to look for motion. Neither will tell you who is standing in each position.

The pressure sensors MIGHT be something an Arduino could handle. The image processing needed for the cameras is probably something you need a PC for.

Or hack an Xbox 360.

You can use a web cam and use Processing to do some image processing. There are a few blob detection libraries.

http://processing.org/reference/libraries/

Definitely a task for a computer, not arduino.