A: 

Maybe you can use jquery impromptu plugin, follow the link for a detailed explanation... in a nutshell, you would be using a form's standard input type password.

Impromptu

Something like this:

var txt = 'Enter your password:<br />
      <input type="password" id="jPassword"
      name="jPassword" value="" />';

function mycallbackform(v,m,f){
    if (v){
      $.prompt('your password is of '+ f.jPassword.length + 'characters');
    } 
}

$.prompt(txt,{
      callback: mycallbackform,
      buttons: { Accept: true, Cancel: false }
});
Jhonny D. Cano -Leftware-
+2  A: 
Philippe Leybaert
+1 Was going to suggest something similar to this.
micmcg
unfortunately type property cannot be changed
gustavogb
@user49687: you're right. Added an alternative
Philippe Leybaert