This extension allows you to get updated quotes for the stocks and indexes that you choose. Go check it on the chrome gallery!
There is a seemingly forgotten url from Yahoo, which is used by this extension to enable auto completion of stock symbols in the options page. However, this API is only accessible through jsonp, and the new manifest rules for Chrome Extensions forbid this method for non https url's (see https://developer.chrome.com/extensions/contentSecurityPolicy.html#relaxing).
To bypass this restriction, I set up a Node.js server that reroutes the jsonp requests as normal JSON requests. The code for the server is in the auto-complete-server folder.
You can do pretty much what you want with the code, which is released under the MIT license.