What unexpected things can I learn about a user from their browser?

Question

I'm giving a class of high school students a demo of unexpected things a webpage can tell about them from their mobile - even if they're not signed in or anything. So far I have picked a couple of things most people would know about, like:

Device OS

Specific handset (unless you're on iPhone, then it's just iPhone)

Language setting

And a couple of more obscure things:

Carrier (hitting a remote service and returning JSONP since js is IP naive)

Battery level / charge status (I didn't even know you could do this until today)

Can you think of anything else cool / creepy in a similar vein that I can dig out of UA / Navigator / etc? Most of them are running Chrome under Android or iOS (which is lucky, not every browser supports the battery thing). The main event is about mobile safety and phishing so I'd like to stick to mobile phones.

Quick edit: for clarity, I'm building out a site they will go to which will actually demo these features - so unfortunately they need to be implemented, at least in Chrome, vs planned / drafts.

Answer 1

You should mention geographic location. A competent javascript library e.g. MaxMind or Google Analytics can be used to pinpoint to geographical location of users.