Some tools never die, and in time gets better...
I created the "KC Tools WP" plugin long time ago, to do my jobs, and still use it. And time to time I add something new. Today I decided to release new version, so everyone can benefit. Now plugin include new and powerful tools. Let me explain:
For your users, there is "debug email", they can send email to you (set your email address as "debug email" inside) from the URL of his sites.
For you, there is hidden function to show $_SERVER array.
But most power tool is in "DB" tab. Now it recognizes when the cell in SQL table saves serialized info, and can show it to you in "readable mode".
Well, hope it will be nice for you. :-)