title: What do I need for a script that detects which device or computer used to visit my website?
body: <p>I simply want to use an AJAX mechanism to track how long a person has been on a web page and whether a logged in, registered user is using more than one device or computer to access that page at the same time.</p>
  
  <p>Is there a way for javascript or jQuery to send a unique identifier for the device or computer at intervals back to the web server?</p>