We are going to augment our Today app with a to-do activity that lets the user add to-do items and associate them with specific locations, such as home, or work. The locations then provide the context, which drives the notifications. This, in effect, makes our notifications context-aware.
For example, if the system detects that the user is in close proximity to the Home location, then to-do items associated with the Home category are presented to the user via the notifications API.
We'll be using the Geofencing API to figure out the location, that is, the context. In essence, this API lets us draw a circle of some agreed-upon radius around a coordinate. In effect, the latitude, longitude, and radius together define a geofence, a circular region around the coordinates of interest. Entrance and exit events signal when the device enters or exits the geofence location. An optional duration attribute delays the triggering of an event for that time interval...