Hello,

Wordpress mantain globals array of variables that contains a lot of useful informations.
There are also a lot of accessible less documented functions.

You can access widgets information with:

$wp_registered_sidebars

$wp_registered_widgets

I think that the right function for you is

wp_get_sidebars_widgets(false);

You can call it anywhere in your theme. It returns an array that you can inspect with a:

print_r(wp_get_sidebars_widgets(false));

There is a nested array (the second) that contains the sidebars list and the active widget for each of them.