The site I have mocked-up does not exist. I want to work on it, but it does not pay, and I need to eat. :-) I am working on a side-project (yes, a start-up) that will provide the income I need to work full-time on the World Politics idea.
I've had similar ideas, mainly focused on holding legislators and their contributors accountable.
It should be really easy to see how legislators voted, and also to see which companies contributed most to those on either side of the vote.
Also, I would include a "I approve/disapprove of this legislation" button. This way, the site could tell something like "You current Senator voted for the bills you support 15% of the time." In which case, you vote for someone else.
Does this site exist? If not, what existing sites do you think are closest to your vision?