I've done, recommended, and been recommended this before and am in wholehearted agreement. I would be remiss however if I did not share a word of caution: that model of pull up bar leaves black marks, and after extended use, will probably dent a wooden door frame. I do not know of a model of that type that does not share this design flaw.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.