In a new post Jonathan Street mentions a new PEAR package that's an API for the Compete API:

After writing about the compete API Hiroki Akimoto contacted me mentioning a proposal he had made to PEAR. Our scripts each had strengths and we decided to combine our attempts and hopefully make something better. After a week or so we updated the proposal with the new code and after a little time for comments and a week for voting the proposal was accepted and on 30th July a new package, Services_Compete, was available on PEAR

This package (currently in an alpha release, version 0.1.0) acts as a wrapper class to connect to and use the Compete SnapShot API.