The Toolmaker's Hammer from Starrett seems like a disastrous idea, akin to bashing in a nail with a camera. The steel hammer incorporates a magnifying glass in the head, apparently allowing the craftsman to easily sight the site for accurately punching a centerline.
The lens it at least suspended in a rubber collar, and as glass in compression is a pretty tough substance, you should be safe. If I needed a magnifying glass to see what I was hammering, though, I'd be more worried about the health of my thumb. $50.
Product page [Starrett via Toolmonger]
