If your mobile device that is running the SmartThings App has location services enabled, you should be able to create an Automation Routine that says when you get within your geofenced area, turn on the AC/Heater to a specified temperature.
Using @Kirk_Brown’s app and handler set, I was able to set this up on my iOS Device and record the routine.
Notice at the 1:30 mark, may Sensi thermostat is set to cool @ 78 degrees, post refresh, it is set to 70 degrees, the same temp I set earlier in the video when creating the routine.
The thermostat updated because the SmartThings app is what handles the geolocation settings, not @Kirk_Brown’s app or handler.
Link to video is here: http://drops.shdc.io/0lxJwJ