I'm pretty sure the accelerometer has to be monitored continuously, with our without Siri. After all, how do you think geo-fenced reminders work? The mostly-low

I'm pretty sure the accelerometer has to be monitored continuously, with our without Siri. After all, how do you think geo-fenced reminders work? The mostly-low-powered accelerometer can wake up power-hungry location services to see if you've left your geofence. There's no reason to have the GPS running all the time (and your battery life would suffer significantly from that).