Let me start this one off by saying this is not an optimal solution, but in a pinch it gets the job done.  Also, I kind of rushed this so there is a lot of code and it could definitely be shortened up if so desired.

Now that that is out of the way, the following script monitors groups that you wish monitor on a white list basis.  This means it requires a lot of upkeep if you are in a rapidly changing environment, but luckily I am not.  It is quite simple to add groups should you need to so that’s a plus.  In the event of someone being added to one of the groups that isn’t on the corresponding white list, you will get an email notification.  I just deploy the script as a scheduled task that runs every hour.  Simple but effective.