A tracking task: help needed

We are setting up a student project for which we need some help.
Any suggestions on how to tackle the problem are gratefully received.

There is a video tape showing a moving person. On his/her arm, there is
a light source, so that what we need to do is to track the light spot
(a classical tracking task). The output of the control system is simply
the xy coordinates of the light spot as a function of time (which will
be further processed, later).

A computer simulation of this is perfectly acceptable, although what we
really want is to use the real data, that is, the video tape.

Any suggestions? Thanks in advance,

Marcos Rodrigues
mar@uk.ac.aber