Consider a simple online booking system, backed with google calendar or speaks ical. Importantly, something that lets their customers pick a time slot, send reminders, etc.

A number of healthcare providers locally do something similar; benefit to the vet is lower admin costs (answering phone etc), potential of online payment to secure the consult, and easy ways to reach their customers for follow up (vaccination reminders for example could be triggered by adding people into a mailing list package, email details gained at time of original booking).

Those are harder to build, but offer clear value and ongoing revenue ($1/booking fee x 5 vets x a year starts to make it look attractive!)