What happens if my Dad goes out the front door in winter on his own to get the paper at the end of the driveway and does not return within a reasonable time?

If the end of the driveway is in the Safety Zone and he goes beyond that point, the Base Station alarms will be triggered and you will get a message. If your device has a Temperature Alert the temperature alert would be triggered depending on the temperature limits you have set. If he fell and your device had Fall Detection alerts, you would get notification of a possible fall.