I don't think this is possible through the core so I'd like an add-on / package that allows me to send an email to a user when they are removed from a group.

I'd like to be able to add a message on the group page that the user will receive when they are removed from that group.

I've attached a mock-up image.

Edit: I know my mock-up doesn't show it but I''d like the message area to be a WYSISYG editor with Source option (see screenshot)