Google, as promised, includes support for add-ons for your browser.
Recently, 
documentation has been published for developers, and now examples of add-ons.
There are three Gmail Checker, Subscribe in Google Reader and BuildBot Monitor. I tried Gmail Checker.
How to install?
1. For this, you need 
Chromium or 
Dev version of Google Chrome, current (2.0.181.0).
2. Right click on the shortcut, select 
Properties and add to the address chrome.exe 
--enable-extensions .

3. Start Chrome :)
4. Additions to take 
here .
This is what the Gmail Checker looks like, on the status bar below, shows how the number of new emails should be.
