This function is ran just before the system process your item deletion.

/**
 * @param $inventory_id
 * @param $data
 * @param $subject
 * @param $message
 */
function my_custom_function($inventory_id, $data, $subject, $message) {
    // Do whatever you want with these pieces of information.  With the inventory_id you can even lookup the item info.
    // You can send info to another database table, send out an email, etc.
}

add_action('wpim_pre_delete_item', 'my_custom_function', 10, 4);