Something like this... just off the top of my head

gistfile1.txt

KbdButton.prototype = {
  installHotkey: function() {
    // Install a single anchor in the body to catch our accessor.
    var accessor = $( "<a accesskey='k' style='display:none; position:absolute;'>" );
    $( "body" ).append( accessor );

    var whichKey = 0;

    var keyCaptureDialog = $("body").append('<div id="captureKeys"></div>').dialog({
      resizable: false,
      height:140,
      modal: true,
      buttons: {
        Cancel: function() {
          $( this ).dialog( "close" );
        }
      });
    keyCaptureDialog.on("keydown" function( event ) {
      if( event.altKey ) {
        keyCaptureDialog.dialog({buttons: "Alt+" + String.fromCharCode(event.which): function() {
          whichKey = event.which;
          $( this ).dialog( "close" );
        },
        Cancel: function() {
          $( this ).dialog( "close" );
        }
      }}});

    $( document ).on( "keydown", function( event ) {
      // If Alt+K was pressed...
      if( event.altKey && event.which == whichKey ) {
        // ...find the parent KBD toggle button.
        var kbdToggle = $( document.activeElement ).parents( ".wmd-container" ).find( "li.kbd-button" );
        if( kbdToggle.length > 0 ) {
          kbdToggle.click();
          event.preventDefault();
        }
      }
    } );
  },