Extract email ids from Gmail

Is there any bot that can extract email ids from a gmail account? I want to extract all the email ids from the incoming mail. It should be able to extract the reply-to addresses, to addresses, from addresses and any other email ids in the text body of the mails. It should be able to filter in or filter out emails too. Like filter out @server to a text file and stuff. Is there any free tool that does this? If there isn't, I'd love it if someone could code it for me (I can help with the idea on how to go about coding). Any thoughts guys?