Here's a simple bookmarklet that will take the URL of the current page you're on and tell SABnzbd to download it. It works great if you're using NZBMatrix and on the page for the post you're wanting to download. Perfect for your mobile browser.
javascript:location.href='http://yourhost:8080/api?mode=addurl&name='+encodeURIComponent(location.href)+'&apikey=yourapikey';
Be sure to insert your SABnzbd API key and hostname (or IP address) into the bookmarklet's code.