Personally I think that the idea of parsing HTTP response headers as a service is one aimed clearly at people who design websites but don't understand how they work on the server side. Otherwise you're paying someone to add extra script load to your site to give you data you already get.

Maybe there's a market for that, but I'd be surprised if HN or any serious tech site would cater to the same demographic.

What's left is the geolocation. At this point I'd think a major USP is relegated to a bullet point in a feature list. I've not seen much in the way of helpful geolocation APIs, and the data needed for this costs money if it's mission critical.

You've got to maintain the database after you've bought it, you've got to run a server for that database, you've got to write a script or an API that exposes it, in JSON format, to a client-side script...

If you're not up for that commitment, or it's not worth the time or money, then surely 'geolocation.js' (as opposed to 'visitor.js') can help you out. And your commitment to it lasts only for as long as you pay.

But for anything else? Well, I'd want a server to save that for analytics, and posting HTTP response data via an XMLHttpRequest is a bit convoluted.