It's an air powered drill that has an air-actuated leg that helps to push the drill steel through the rock. It's the type of drill used to drill blast holes in vertical rock faces or in building columns. They can be rented at some equipment rental stores, but you have to check around in your area. Here's a link to a dealer:
http://www.mwdrill.com/product.php
or you can try a google search under "jackleg rock drills" and you'll probably get a gang of hits.
I've used drill steels from 2' up to 8' in length with 1 1/2" to 2" holes. It's just an idea.

neyc, you could always just use a jack leg rock drill, you would hve to probably drill more than one hole and then chip out the overburden, it's not as neat and clean but it would be cost effective.

Yeah, drilling through granite can get expensive.

Another thought, is it feasible to penetrate the wall just above the footings, or is there floor slab in the way? Just a thought...