It seems like this would be an important attribute to detect as it seems that all of the other solutions are hacks. I mean, we can detect the exact device a website is using to view a website. It only makes sense that there should be a way to detect a screen reader.

I'm not trying to be biased, but it seems that a meta tag or something similar can direct an appropriate style sheet or even an appropriate HTML doc that would be more beneficial to those with screen readers.

I would even go one step further and say that there should be a style sheet for those with major color blindness and contrast issues.

It seems as if these setting should be assigned on the client side and determine the correct way to present the content.