For English (and some other languages), it's quite easy to find online tools that give a readability index of a specific text. Naturally, this doesn't necessarily match actual experience of reading the text, but it does seem to be reasonably accurate. Here's an example of such a tool.
My question is: Are there any similar tools for Chinese?
If not, are there any other practical ways of automatically estimating the difficulty of a Chinese text? I have tried crude methods such as using an annotator that can show vocabulary at different HSK levels, which gives a clue to the difficult of the words in the text at least, but that's not really what I'm after. However, if anyone knows of partial solutions to the question, that would be interesting anyway.