Ok first off is this is possible I think it would be an awesome addition to Appointments+ making it just perfect for my business and others that travel such as hair dressers, photographers etc.
The idea is based on below
But with a slight tweak. A client would book an appointment and the zip code / post code field would be mandatory.
Next client would come along and pick their appointment and again type in their post code.
Next google (or something else) would calculate the time taken to drive between the two locations and flash up a box saying something like
"I'm sorry but the previous appointment location would mean I require 25mins to drive to your location. Would the next time slot of Xpm be ok?" This bit would be flexible dependent on how long it takes to drive from A to B.
The user could then click yes and Appointments+ blocks out the travel time and appointment. Or if the user clicks no it just asks them to select a different time.
The icing on the cake would be a hover box on the time boxes which highligted different post codes so a client could see one which was close to theirs. My regular clients could then book appointments when they know I'm in the area.
Anyhow I think the addition would be awesome if at all possible!