I looked for a simple debugger to use in the fronted, and discovered PHP-ref.

I like to keep things simple and clean. I like devel when using simple debugging on the frontend (for more advance debugging I am using xdebug), put devel adds a lot of overhead - like many drupal modules it tries to cover a lot of issues, and therefore it adds a lot of things you maybe not need. So I tested some of the debuggers you could use with php in the frontend, and I really like PHP-ref - simple and clean, just the way I liked it. So now I have wrapped it out to a moudle - Ref debug. With it you could do debugging on entities and direct in code as an replacement for devels dpm() - instead you use r(), and to that you could add functions, variables, classes etc. You could check it out over att drupal.org.