Browser Details allows you ‘to see everything you need to know about your client’s browser – and have that information sent directly to you’. After registering you’ll get your own browser.details.com subdomain. If your clients are having problems with one of your web apps you can simply direct them to that subdomain and Browser Details will store (and mail) their environment information such as which browser they’re using, the OS they’re on, their screen resolution and so on.
Browser Details offers a free basic plan. For €7,49 you’ll get your own CNAME, multiple eMail recipients and your own logo.