How to programmatically retrieve the total number of Google +1's for a URL

Question

Now that Google has officially released their +1 button for websites, I'd like to find a way to retrieve the total number of +1's for a specific URL programmatically.

For example, I'd like to access this value independently of the +1 button for use in tooltips, as shown for RSS subscribers below.

More information on the +1 button: https://code.google.com/apis/+1button/

Answer 1

Google+ metrics: Activity by URL gives the sum total of all +1's for a URL, as well as the number of +1's for a specified time frame. It is only accessible via Google Analytics on the webmaster dashboard.

EDIT
Google now has an API for retrieving Google +1's. It is still in early developer preview though. Google+ History API tells you how to sign up for the preview.