Well, the site you referenced was written in PHP, so I'd say yes, it can be done. But I don't think you are going to just find the scripts for this online. It's definately going to have to be a custom job. You'll need to research the sites you are going to be comparing prices from. Some of them will offer XML pulls (I remember hearing Amazon did this). Some you will be able to post POST info to, so may let you use sockets, etc...
You could also contact the site you referenced, and see if they will share some code, or maybe let you connect to their search..