Follow Path and Track To constraints together I've got a camera with a follow path constraint:



Throughout the animation, I'd like to be able to make the camera point at something in my scene, rather than forward along the curve. For example, I'd like to make the camera look at Suzanne as it rounds the corner in the top right of the screenshot. This should be a smooth transition from pointing forward along the curve, to point at Suzanne, and back to forward along the curve.

I've tried parenting the camera to an empty, and tracking to the empty. The idea was that the empty would come along for the ride with the camera, but it could be moved off toward Suzanne as it gets close to the corner.
With the following constraints the camera follows the path, with the influence of the Track To the camera can be directed to the target object. The influence can be keyframed by hovering and press I. 





Demo blend