Modify Userpoints List FormTo Show Entity ID? How does one modify the List used to display userpoints?

eg.

http://example.com/user/123/points

I'd like to be able to modify that (table) to display the Entity ID (the source transaction id). 

Apparently, it is generated as a form/table in the Userpoints module, right? I think that SQL field is already part of the query. But is there a way to hook into that form and add columns without hacking the module? How is that done?

The form ID is userpoints-list-transactions

I see a hook in userpoints.api.php

function hook_userpoints_list_alter 

so I created a function in my own module (which I know is loading and working for other functions)

 function jch_utilities_userpoints_list_alter(&amp;$output) {
    dpm($output);
    }


...and it never fires. What am I doing wrong?
Do you have the Devel module installed? dpm() won't work without that.