User12817 posted@AshleyKurian?,
I would suggest reading through: http://docs.xamarin.com/guides/android/platformfeatures/mapsand_location/
As far as geofencing, it shouldn't be too difficult to make shapes around the points that you define. For simple squares, you can already set that up in the google maps API.
https://developer.android.com/training/location/geofencing.html
You will have to port this Java example to C# however, and it shouldn't be too difficult!