voting on comments

I have been searching high and low for a simple voting plugin that does the following:

For certain posts, the author has the ability to “Enable Voting.” Once the author makes a comment and enables voting, a checkbox appears next to the comment.

Then, for all users logged in, they have the option to go through and vote for which comments they think are the bests. The logged in user would check each checkbox of the comments they think are the best, and then have the ability to click a button and vote.

Obviously, this would require a separate catagory in the wp_comments section called something like comment_vote. This value could be then incremented by 1 each time a logged in user voted for that comment. I also would hope that there was some way of preventing re-votes (ip address cookie).

If this sounds familiar, it is basically what fark.com does on their photoshop competitions. Seems like a useful plugin that could be developed. I am new to the wordpress scene and have not seen any other plugin with this functionality.

Any help or comments would be appreciated.