I use ibeacons for this, which work pretty well for detection but are a little tricky to get into SmartThings. So automations might take a minute or so to run, which can be annoying if you’re standing there waiting for the door to unlock. It also requires a paid third party app. But if you’re interested in that method, see the following. It says UK, but the answer I gave also works for the US. (The topic title is a clickable link.)
A better but more expensive alternative with SmartThings is to get a smart lock that detects your presence with Bluetooth (August or Yale by August are good, but there are others) and then trigger off of the door unlocking when the mode is away. That’s quicker and easy to set up, but if you have multiple people in the house routine design may be a little more work.