I make Google maps for every city I visit with pins for strip clubs, massage parlors, red light districts, brothels, and friendly hotels (as well as restaurants and non-hobby info). You could easily do it for clients -- and it doesn't even have to be a pin for each client. You could have different style pins for different numbers of clients (small red pin for 1-2 clients, medium yellow for more, and large green pin for many), or different symbols for clients with different requests/preferences. Google Maps can even be exported to many cars' GPS systems. PM me for assistance if you need.
As an example, here's a map I made for my upcoming trip to Germany.
https://drive.google.com/open?id=1d4...Iw&usp=sharing