I buil this tool to help people to accurately answer (by not having to actually answer) the question of "what browser are you using?" when writing to me with a support request or a bug report.
After filling out a form with just a single field for their name, the script emails their User Agent, IP Address, and (if JavaScript is enabled) the results of their Modernizr tests.
PHP 5, Composer and a Postmark API key.
This repository includes a build of Modernizr with the tests I like to have access to. You can build your own on the Modernizr download page.
This tool is released under the GNU GPL v3.0.