India Broadband Forum user Amit has released a browser extension named Airtel Data Usage Info for Google Chrome browser.
Development thread on India Broadband Forum
This is targeted at the users of airtel broadband connections in the Indian market. The app fetches the information from the airtel smartbytes page and shows you your remaining data for the current billing cycle on the right side of the omnibar.
You can click the icon to get a more detail information fetched from the same source. The app lets you set the refresh time period for the displayed information.
If you are using airtel broadband, you would love to have it installed on your browser!