If you only care about setting the timeout upon an exit event, just update that geofence once it triggers an exit. This is a very basic example of how to do this, with notes on how to improve it. Once you get this working, you could essentially have a keep alive for geofences, only timing out when they haven't been triggered in some time.
public void onReceive(Intent intent) {
//.... your code ....
GeofencingEvent event = GeofencingEvent.fromIntent(intent);
if (event.getGeofenceTransition() == GEOFENCE_TRANSITION_EXIT) {
//This assumes you only worry about one geofence, but there may be others in this list...
List<Geofence> geofences = event.getTriggeringGeofences();
Geofence geofence = geofences.get(0);
String id = geofence.getRequestId(); //Do a check to see if this is the geofence you want to modify.
//Either send the id to the class that handles adding geofences, or have a reference to your GoogleApiClient here.
//Assuming you have GoogleApiClient reference here...
Geofence.Builder geofenceBuilder = new Geofence.Builder();
geofenceBuilder.setCircularRegion(lat, lon, radius);
geofenceBuilder.setExpiration(1000000);
geofenceBuilder.setRequestId(id);
geofenceBuilder.setTransitionTypes(transitionTypes);
//The GeofencingRequest class is parcelable too, so this be another option to send your request to a class that handles google api calls.
GeofencingRequest.Builder requestBuilder = new GeofencingRequest.Builder();
requestBuilder.addGeofence(geofenceBuilder.build());
requestBuilder.setInitialTrigger(initialTrigger);
LocationServices.GeofencingApi.addGeofences(apiClient, requestBuilder.build(), pendingIntent);
}
//... the rest of your stuff
}