You can add Walk Score to your listings following the steps here:
1. Sign up for an account with http://www.walkscore.com/
2. Generate an embed code for your listing's walkscore by typing in the address of the listing, setting the size and click "Get embed code"
3. Copy the embed code, and go to your website's control panel.
4. Click on Listings tab
5. Click the listing
6. Click Custom subtab
7. Under Custom Detail Content, Click the HTML icon for the HTML source box to pop up
8. Paste the embed code
8. Click "Update Custom text"
Congratulations! You were able to add walkscore to your listing!