Hook vs. Helper

Thank you for starting this plugin!

I have a small suggestion for improvement:
Currently, the plugin establishes a hook that will be triggered with every page request - no matter if the detection is needed or not.
To detect the browser only when it's needed, you should probably do this solely in the helper and cache the result in the stash.

In addition to that, it's now common to use "Mojo::Base" instead of "base", as it does more nice things (strict, warnings, features, utf8 ...) and though is future-proof for use in conjunction with Mojolicious::Plugin.

With best regards,
Nils