Confirmation pop up on login submit
Sounds like some simple Javascript. E.g. by the help of JQuery you could bind a click/submit function on the login-form, show a confirm-window ("Would you really like to log in?") and if this is confirmed, submit login-data (or not).

Such a function could(!) look similar to this:

$('#user-login-form').submit(function(){
 var r = confirm("Would you really like to login?");

 if (r == true) {
    return true; // submit form-data
 } else {
    return false; // stay on page
 }
});