Several years ago, we released a little FireBug plugin called YSlow. This tool allows you to analyze your Web pages for performance problems. Among the things that YSlow can do includes measuring page-load time, and beaconing its results back to a home server.
One thing's been missing though. While these tools let us measure our pages in the lab (that is, your dev box), what the end user actually experienced was, for the most part, unknown. With the number of variations in operating systems, browsers, plugins, ISPs, network configurations, geography, and microwave ovens, it's impossible to simulate all possible combinations that a visitor to your site might have.
To fill this gap, we're releasing a tool called Boomerang.
Boomerang is currently in beta, and we'd love to have more people working on it. So go check out the code, use it, fork it, patch it, and tell us how you like it.