The best way to what you want in a Desktop app is using User API Keys.
You do need a web interface either in the app or by opening the browser, but if you make your app a handler for the protocol used by the mobile apps, you can easily have it get the token that way and only have to use the browser again if the token expires or they use a different device.
My personal experience with this is that using the User API keys is a much safer and simpler option than trying to use the session end points. 