Is there an easy way of doing "analytic ambient occulsion", like in this demo?

A lot of you have probably seen this. What I really like about it is the dynamic ambient occlusion, it creates a fake light bouncing effect that really give the scene a lot of realism. To see what I mean, move the ball closer to/further away from the walls and floor of the pool.

Is this simple to do in Unity?

If you have Unity Pro then yes, you could attach the SSAO component or create something similar using it as a base

Without Pro you won’t get any dynamic fullscreen effect at all I fear