Notify admin during login

Yes – there several hooks directly in the WP-Members login function, but I’d probably hook it to the wp_login action, which would fire no matter when/where the user logged in (of course that means you probably want to add some logic to exclude admins since it would fire when you log in as well).

Your action function would just need to retrieve the user’s email address (the WP user object is passed to the wp_login action so you’d have access to any user info via ID) and then send a message using wp_mail().