Apps like Llama let you use location-related properties (such as Wi-Fi network visibility) to trigger automation actions such as putting the phone on silent, but they do this by running as a background service and polling for Wi-Fi networks or directly for location.
The Google Play Services library contains a geofencing facility, which allows apps to define geofences and to be started in response to (the phone) entering or leaving those geofences.
Since Google Play Services already needs to run and update my location for things like Google Now and Location History to work, I'd like to be able to use this to have it automate things on my phone, without having an extra service in memory all the time and running periodically. Is there a way I can set this up on my phone? Perhaps there's an app like Llama but using Google Play Services geofences instead of Wi-Fi, or a way to configure Tasker so that it only runs when triggered by a geofence I define. (I've never used Tasker.)