I have had a feature idea i've wanted to implement using ajax for a while.

Consider that you are looking at an auction page. In the event that a new bid is placed while someone is looking at the page, I want the page to update without a refresh so that the new bid and the new bidder are now visible.

Now you might think that this is impossible, but I beg to differ. I got the idea here: http://ht.bidz.com

As you can see they are somehow using flash to connect to their backend and update the time + amount whenever a bid is placed.

Now i'm guessing that its currently impossible to actually update the page unless you are constantly checking for changes in the database. So I thought perhaps running a script every few seconds to determine if there is anything new to show. The problem I guess will be overhead.

Does anyone have any ideas on how I could create such a feature?