There is a review of Senator Who up at iPhone J.D. showing exactly how Senator Who can be used: if you run into someone walking through the Capitol, open up Senator Who and enter as much as you can see about the person, and Senator Who will show you the Senators that match. If you’re not sure whether the person’s a Democrat or Republican, that’s fine. Enter what you know, and Senator Who will sort it out.
As Jeff mentions in the review, I am definitely planning an update to be released in January when the new Congress arrives. I also hope to have a small update in the next couple of weeks to include the senators elected in special elections, since they’ll be serving in the lame duck session.
A version for the House of Representatives is also in the works, and I’m hoping to have it ready for January (can’t promise, though).