Presence continues to be one of those things that everyone would like and no one has really solved yet. you will find a lot of discussion forums about different ways that people have approached it.
Right now there are basically two different classes of devices.
Class 1: GPS
GPS-based devices use the tracking facility that’s built into your phone. This has a minimum radius of about 500 feet. However, there can be some flakiness because it’s based on the last cell tower that you connected to and there can be a balance affect where it’s going back-and-forth between two different cell towers which results in reports of you moving rapidly back-and-forth between them when you aren’t, really. So a lot depends on exactly where your home is compared to the nearest cell tower. If you happen to be just about equally distant from two or even three towers this can cause more problems then if you’re just close to one. This is one reason that phone based geo presence may work great for one person but not work for another.
class 2: local connection via zigbee, Bluetooth, or Wifi
The second class is based on devices that connect to something that is physically located in your own home. These are much more precise, but generally have a much narrower radius. Bluetooth devices like I beacons have a radius of about 30 feet maximum, but can also be set much smaller, even to within a few inches. Zigbee devices, like the SmartThings arrival sensor, have a non-adjustable radius of about 50 feet. Some people use Wi-Fi which has a non-adjustable radius of about 150 to 250 feet.
You mentioned an “Aeon presence sensor.” I’m not familiar with this device, and to be honest I’d be very surprised if Aeon made a presence sensor. Aeon makes zwave devices, not Zigbee, and for technical reasons zwave is not typically used for presence sensors. By any chance did you mean the SmartThings branded presence sensor instead? Or the iris branded presence sensor (which does not work as a presence sensor with SmartThings).
multiple device Approaches
I need presence detected within a very specific range because of what I call the bus stop problem. I use a wheelchair. It can take the bus driver several minutes to unload me at the bus stop. For that reason, I don’t want detection to kick in too early, as that would cause my door to unlock while I was still on the bus.
I ended up using a combination of a Bluetooth I beacon and another device, in my case a zigbee contact sensor on my front gate. The front gate device sets my house into coming home mode. Then when I get to the base of the wheelchair ramp at my front door, the IBeacon triggers the actual arrival events. The sequence keeps the arrival events from being triggered as I leave the house. There is a thread discussing this and some other possibilities.
The basic idea can be applied to many different kinds of devices from both class one and class two. You could definitely have your regular iPhone GPS presence act as the first detection and then use a class two device for the second.
Since you mentioned an iPhone, you do have an easy-to-use option which those using an android phone do not. There is a very nice third-party rules engine app for use with Smartthings called SmartRules. It cost about seven dollars in the App Store and there is a two dollar add-on that allows you to then Use Ibeacons as presence indicators with SmartThings. The developer @obycode , is a very active community member here. Check with him to make sure that the Beacon option is currently working, but I would definitely suggest looking into it.
Other community members have used other options, including wifi detection. Most of those projects require more technical skill. If you just search the forum for presence you should find a lot of them.