idxList.html

// list
var list = [
  {
    letter: 'A',
    members: [
      'Ari Lerner',
      'Abe Linc'
    ]
  },
  {
    letter: 'D',
    members: [
      'David Wu'
     ]
  },
  {
   letter: 'Z',
   members: [
     'Zen Master',
     'Ziff Davis'
   ]
  }
];

// template
<ul>
  <div 
    class="item item-divider"
    ng-repeat="letter in list">
    {{ Object.keys(letter)[0] }}
    <li ng-repeat="contact in letter">
      {{ contact }}
    </li>
  </div>
</ul>