Recent activity on my Gmail just revealed that there's this app "Authorized Application (225019099301.apps.googleusercontent.com)" from IP address 184.108.40.206 assessing my Gmail.
The IP address is from a Amazon server ec2-54-235-159-144.compute-1.amazonaws.com. (IP Lookup).
And blacklist check (http://whatismyipaddress.com/blacklist-check) shows that the IP is clean too.
Clicking on the "Manage Account Access" didn't give any information on the application "225019099301.apps.googleusercontent.com".
After Googling, it appears that the app is Mailbox (source: http://productforums.google.com/forum/#!topic/gmail/9LVW_etXyTE)
To make things easy, Google should show the applications with their ID.