What you posted looks like it would work just fine, my thought though is what are you drilling that's going to require you to be that accurate? If you need to be that accurate you might as well invest in a cheap drill press.
We bought a $59 Harbor Freight drill press about 10 years ago. We've easilly drilled 10,000 holes with it and never had a problem. Drill presses are fairly simple technology.
I would go with a small bench mount drill press like bayshore and Pat mentioned above...you can bolt it to a 18" square of 3/4" plywood and easily take it to the offsite job in the back of your pickup....Way more accuracy and power than the clamp the drill rigs....
Go down to your local pawn shop you can probably buy a small drill press cheap haggle on price cause there's more pawn shops down the road. I worked for a guy that bought a hand drill Press attachment and the drill doesn't always fit in well so when you hit something hard the drill cocks sideways and if your drill has a gears in the head and not a direct drive motor shaft to the chuck you will get sideways movement in the chuck. If you don't have multiple drills you have the hassle of installing and removing the drill. good luck shopping
I have a Craftsman unit for a portable drill. I got it to do some hobby milling for which it worked well enough. If I was to do any more than that, I would look at a cheap benchtop drill press as for most things, they would be more than adequate. I usually buy heavy duty professional grade tools but you have to equal out the amount of use it will get.