I just thought i would post about a simple piece of exercise equipment that I bought for my son, and that I have found that I like, too.
My son does quite a few pullups, and his friends like trying it. I put it in a door in the main hall, so it is right where we walk by all the time, so, it is convenient to try a few when you walk down the hall.
I can't pull myself up - but I just hang and try to pull up, so I guess i'm doing isometrics in a sense. and I've seen a little difference in just a week. a tiny difference.. but some.
I think the price is reasonable. It seems to be well made, sturdy.
anyway, here is a picture:
some amazon reviews: