This is a simple implementation of Agile Planning Poker in your browser.
After sharing a unique URL with your remote team members, every user can enter their estimation. The result will only be revealed once everybody has given an estimate.
http://estimation-poker.pixelistik.de
However, this is running on a very small Heroku dyno, so it might be slow.
After opening the page, copy the URL from the address bar and open it in another browser session (or actually give it to a colleague).