New in the GMail Labs is a signature feature that will report where you are currently located. This was part of a 20% project for Marco Bonechi, Software Engineer for GMail. One of the questions he has received often is “where are you?” since he travels around quite a bit. This new feature will include a line below that says “Sent from: [city name, state, country].
To activate the feature, click on Labs within the Settings Tab and activate “Location in Signature.” Then go into your signature preferences and click on “Append your location to the signature.” The signature will use your IP address to figure out where you are located so it may not be correct everytime. For example, my IP address reports me as being in Southfield, MI instead of Ann Arbor, MI since that is where my ISP is based.
However if you want to make your location more accurate, there is a version that supports the locations module within Google Gears. Gears will report where you are located based on the wi-fi access point. In every e-mail you write, you can delete the line that reports the location.
[via GMail blog]