ryzenyui

Yes. You cannot have a windows service interact with a user's sessions. Ask yourself the following questions:
 
On what user session the service should start the application? What if there are multiple user's logged in? Does a windows service really need to know about a user, afterall it's a service not an application. You want to create a scheduled task that is set to impersonate a user and start an application. You will also want to set it's schedule to manual, then invoke it from the mobile app.
 
Good luck.