JavaScript Bookmarklet to add-up all the estimated checklist items on a card in Trello.

trello-checklist-sum.js

var $lists=$(".checklist");
$.each($lists, function( key, value ) {
 
  var $lName = $(value).find(".checklist-title h3");
  var $lNameInput = $(value).find(".checklist-title input");
 
  var $items = $(value).find(".checklist-item");
  var $tot = 0;
  $.each($items, function(key, value) {
      var $itemText = $(value).find(".checklist-item-details-text");
      var $itemEst = $itemText[0].innerText.match(/\(\d+\.?\d*\)/g);
      if ($itemEst) {
        $itemEst = new Number($itemEst[0].replace("(", '').replace(")", ''));
        if (!isNaN($itemEst)) {
          $tot += $itemEst;
        }
      }
   });
   $lNameUp = $lName[0].innerText.match(/^[^\(]*/i);
   $lNameUp += ' (' + $tot + ')';
   $lName[0].innerText = $lNameUp;
   $lNameInput.val($lNameUp);
});

Instructions for use:

1. Create a bookmarklet which contains the above code... or drag the link from this page to your bookmark toolbar.
2. Go to a trello card
3. Create a checklist
4. Add some items with estimates added in brackets e.g. (0.5)
5. Click on the bookmarklet and see the checklist titles update with a total of your estimates

Note: If estimates aren't fixed, just add a ? or some non-numeric character into the estimate and they'll be excluded from the sum

Gist updated for recent Trello changes

well done! Could you please advise how to aggregate now checklists to card name?

Then Scrum for Trello plugin will be compatible