Snorricam

A SnorriCam (also chestcam, bodymount camera, bodycam or bodymount) is a camera device used in filmmaking that is rigged to the body of the actor, facing the actor directly, so when he walks, he does not appear to move, but everything around him does. A SnorriCam presents a dynamic point of view from the actor's perspective, providing an unusual sense of vertigo for the viewer.

It's how they did this to Harvey Keitel (Mean Streets, about 58 seconds into this clip).

And this to Sir Digby Chicken Caesar (The Mitchell and Webb look).

Here's how you make a rig for a Snorricam, but I recommend turning the sound down because the American kids are really annoying.