I wrote a quick-reply bookmarklet for Twitter. It redirects the browser to your specified URL with the tweet’s permalink as a parameter. This should work for selected tweets in your timeline, specific account’s timeline, and even the silly modal-permalinks.

Copy and paste the below as a bookmark, changing http://example.com/endpoint/?url= to your desired endpoint.

javascript:(function(){if(document.location.hostname=='twitter.com'){var endpoint='http://example.com/endpoint/?url=';var container;if(!(container=document.querySelector('.selected-stream-item'))){if(!(container=document.querySelector('.permalink-tweet-container'))){alert('Could not find tweet permalink. Are you sure a specific tweet is selected?');return false;}}var in_reply_to='https://twitter.com'+container.children[0].getAttribute('data-permalink-path');document.location.href=endpoint+encodeURIComponent(in_reply_to);}else{alert('You’re not on Twitter!')}}())