Background service for xamarin forms app

I have an existing xamarin forms project that needs a background service that will notify the user and application of device location changes and time. The app needs the service to query for new activities based on either time or geographic location. If the app isn't running, the service will still need to check for activity updates and show a notification. When the user clicks the notification, the app will show the newly retrieved activity. The service needs to start automatically and shouldn't require the app be running. When the service triggers, the user will be notified on the status bar if the app isn't in the foreground.... if app is in foreground, the application will present the results from the service. I really just need a working clean simple sample application and service that I can use to use for reference in integrating into my application.