Kalman filter for tracking obstacles
You might consider a particle filter.  Here's a link to a paper I wrote about tracking objects in video using a particle filter.  The great thing about these is that objects can be tracked through temporary occlusions.  The trick with using a Kalman filter here is dealing with the nonlinearity introduced by the edges of the video field, and casting your measurement model as a linear combination of your states (presumably x,y location).  The Unscented Kalman filter is another route you could go, it doesn't require linear models.