The URL scheme allows you to pass a postcode into the app that you want to submit to the database. 

Application homepage: http://blog.johnmckerrell.com/ifreethepostcode/
iTunes link: http://itunes.apple.com/app/ifreethepostcode/id296156549
HTML Link example: <a href="ifreethepostcode:L1%205AP">Add L1 5AP to freethepostcode.org using iFreeThePostcode</a>
Native application URL string example: ifreethepostcode:L1%205AP
Extended example:
Tags: publicdomain postcode

The app assumes that the two halves of the postcode will be separated by a space.