ion-nav-bar with an angular element

I would like to know if there is any way to have an angular element in ion-nav-bar. Basically I am having some info displayed in nav-bar which can change based on actions on few of the pages. So I need to have some sort of control over it from all controllers or from service. How can this be acheived ?

 <ion-nav-bar class="bar-positive nav-title-slide-ios7" align-title="center">
    <ion-nav-back-button class="button-icon ion-arrow-left-c">
    </ion-nav-back-button>
     <ion-nav-buttons side="right">
       <span  class="ion-bag colBlk"></span>{{count}}</span>
     </ion-nav-buttons>
  </ion-nav-bar>

The count variable here needs to be shown on all of pages and could be modifed by actions on some of the pages.