You can add custom buttons to the app header using the header_buttons block. Use anchor/link tags for the button and wrap it in a div with the class header-button. For buttons with the gliphyicons, add the glyphicon-button class as well.
Ever have trouble using a modal in a Tethys app? Use the after_app_content block for modal content to allow them to function properly. See: Bootstrap Modals
Add tooltips to any element by adding the data-toggle, data-placement, and title attributes to the button. See: Bootstrap Tooltips