One thing that I would point out about the script you intend to write is that it requires an awful lot of maintenance (when sites change layout) and is frequently not very reusable. One solution that I tried is Mozenda (http://www.mozenda.com). The have all the stuff you're looking for (i.e. visual, browser-based tool, writing to XML) but also have error handling and notifications, so that if an agent breaks you'll know and be able to fix things inside the visual tool.