Write an Android application - Imitate incoming + outgoing SMS message [fake SMS]

I require a simple Android application thats runs on Android 5.0.1. A fake SMS has to be pretended to be send, and another one, with few seconds delay, pretended to be received. All this without network/provider usage. Basically the outgoing and incoming text messages should just be written to androids default sms application's database. The technical background information can be found here: [login to view URL] . The new sms app has to be temporarily set as default sms app, as long as your app is running -> android requirment since KitKat. ([login to view URL]) The text for the outgoing SMS can be hardcoded in the source, whereas the text for the (fake) incoming SMS depends on parameters set by the user in the android activity. Parameters are: number to who to send, number from where the SMS came and the SMS text. These 3 parameters shell be saved as default values in EditText-controls in a 'settings' tab. The text parameter shell also contain the current time and date, as well as one more parameter selected by the user via a spinner-control. The values of the spinning control for the moment are just: A, B, C, D, E. But the picked value must be present in the SMS text. GUI consists of a tabcontrol with 2 tabs. tab1: Spinner control + Send button; tab2: editTexts for receiver phone #, sender # number, and message text. Thats it, pretty sharp and simple -> low budget project. Preferred coding language is C# (xamarin), but java is ok too.