If you are doing it from the parking lot you don't need RFID/BLE/NFC you can use GPS. If you want to do indoor proximity via your app you can use a beacon with the sdks for iOS (https://developer.apple.com/documentation/corelocation/deter...) and android (https://developers.google.com/beacons/). Estimote is probably one of the most popular beacon hardware makers https://estimote.com/ There are many.

If you really need to do this without a customer app, that has location services turned, on then you will need to use some service provider like kontakt.io. If you search for indoor location tracking there are lots of them.

Also note there are some privacy issues here. I wouldn't want to carry around a BLE card just so the staff at a petstore know that I am in their parking lot.

Also there is the cost of giving these to users, ultimately the customer will have to cover that cost, which I wouldn't want to do.