The Time Off mobile app generates the email content and loads the default mail client on the phone.
The phones mail client is used to send the Time Off request to the supervisor.
The supervisor clicks on a link in the email. This will load a webpage and allow them to Approve or Decline the Time Off request.
The Approve or Decline response is communicated back to the phone via a Push Notification.
The phone automatically gets the Push Notification and records the response from the supervisor.