Booking time at the hair salon or dentist's can be a decidedly low-tech affair. You often have to do it over the phone, and you may not even get a courtesy call, let alone email. That may not be an issue for much longer now that Square has just launched its Appointments service. The system lets you request an appointment through a simple web form that automatically adds to a shop's calendar. After that, you can get email or text reminders that will help you arrive on time.