Quickly recording number of indexed pages

Hello folks,

While I’m aware that the “site:” function in Google returns only a fraction of what is shown in WebMaster Tools, I’m still interested in the realative number of indexed pages for a site for a given keyword.

Is there anyway/tool that does this?

For example, for the term “widgets” it would return back the number of indexed pages for the top 10 ranking sites.

Or does this need to be done manually?

Thanks in advance!