http://www.entropiatracker.com
Answer to the first question you will ask: Yes its real time.
Second question: do a google search for OCR.
Third question: If its legal to take screenshots of
PE, this is legal.
Fourth question: I dont know what you can use it for - prehaps you can see trends before there is a large HoF on a mob.
(Edit: New URL thanks to 711)