I built a little tool, which I thought HNers would find fun. You can play with it here:
http://checkintext.appspot.com/
Follow the instructions at the top, and you'll appear on the page.
If you're on a smaller screen, you might benefit from zooming out.The story behind it is over here: http://www.ousbey.com/blog/check-in-app
Do let me know what you think!