I've used the Iron Gym pull up bar while visiting at a friends house in Portland. It's no different than any pull up bar you could find at a gym. If you don't have the upper body and back strength to do pull ups, you might want to start on a free motion lat pull machine and build your strength up to your body weight.
Another option and by far my favorite apparatus for Body weight training is the TRX suspension trainer. It's good for an all over body workout. I have a link to their site on my website.
I hope this helps.