This extension provides a local eBay auction sniping feature in a web browser.
It will automate bidding on your behalf just before the end of auction.
Unlike other sniper applications this extension doesn't need your eBay password so it won't be disclosed on any server.
All needed is an opened web browser tab with an active ebay session (this tab doesn't need to be visible).
PowerSniper comes with a free and a premium version.
Check out differences here.