I use an IBeacon on my wheelchair. Same idea. I don’t use just regular phone presence because of what I call the “bus stop“ problem, where I’m sitting on the bus half a block away waiting for the driver to unload me and my door opens sooner than I want it to. IBeacons have a near, medium, and far range and a medium works very well for me. I can have it trigger right at the base of the wheelchair ramp.
You can use the Home+ app to integrate it into HomeKit or use Geofency to create a webhook that you can use with webcore or Ifttt. So the set up might take a little thinking through and a third-party app, but it can be done. 
Discussion in the presence FAQ: