At this time Gantter does not have an app. This is on our roadmap but we do not have a set date on this release at this time. If you are looking to sync your teammates calendars with Gantter task, we are integrated with Google. We are able to sync with Google Calendar and their task will be linked to the due dates. If you use Google Calendar already please note that there is a iphone app for the Google Calendar and Google Task.