Google today launched an Activity Report for all its users, this is an opt-in feature you need to sign-in to the service. Once signed in Google sends an activity report every month to its users, the report is password-protected and includes insights into use of Google services by you.
The report includes your activity across Google services, like email activity, how many emails you have sent compared to last month, what web searches you did, what are the top queries etc.
You might wonder what use is this activity report, it gives insights into how much you are spending online using Google services, like personal analytics for your Google life. The report also shows if you are signed in to Gmail from unknown locations, that way you can see if your account has been compromised, you can change the password immediately.
It also shows how you spent your time this week in a nice pie chart, 23h at work, 62h at work and 83h out. You need to be checked in using Google Latitude for this to work though.
Go here to sign in for the activity report, it will take few day to generate report for you according to Google, but for some the report came with in few minutes.
Source: Google Blog