I have been playing with this issue today, I figured I would share my results...
Using the example from jQueryUI tooltip, custom styling and custom content
I wanted to have a hybrid of these two. I wanted to be able to have a popover and not a tooltip, and the content needed to be custom HTML. So no hover state, but instead a click state. 
My JS is like this: 
       $(function() {
        $( document ).tooltip({
            items: "input",
            content: function() {
                return $('.myPopover').html();
            },
            position: {
                my: "center bottom-20",
                at: "center top",
                using: function( position, feedback ) {
                    $( this ).css( position );
                    $( "<div>" )
                            .addClass( "arrow" )
                            .addClass( feedback.vertical )
                            .addClass( feedback.horizontal )
                            .appendTo( this );
                }
            }
        });
        $('.fireTip').click(function () {
            if(!$(this).hasClass('open')) {
                $('#age').trigger('mouseover');
                $(this).addClass('open');
            } else {
                $('#age').trigger('mouseout');
                $(this).removeClass('open');
            }
        })
    });
The first part is more or less a direct copy of the code example from UI site with the addition of items and content in the tooltip block. 
My HTML: 
   <p> 
       <input class='hidden' id="age"  /> 
       <a href=# class="fireTip">Click me ya bastard</a>
   </p>
  <div class="myPopover hidden">
       <h3>Hi Sten this is the div</h3>
  </div>
Bacially we trick the hover state when we click the anchor tag (fireTip class), the input tag that holds the tooltip has a mouseover state invoked, thus firing the tooltip and keeping it up as long as we wish... The CSS is on the fiddle... 
Anyways, here is a fiddle to see the interaction a bit better:
http://jsfiddle.net/AK7pv/