Remote Appointment Calender for Android

I need an "appointment calendar" CLASS for existing Android app. This project is not a whole app, just an android Class/XML that will be added to an existing LARGE app. Here is an example of how the appointment calendar will work using a "doctor/patient" as an example..... For example let say you are a doctor, your "appointment calendar" shows when you are available for appointments. The doctor can block out times on the calendar when hes in the office, and only during those times appointments can be set. The patients can see the calendar showing existing appointments from other patients, and free time where appointments are available. Patients themselves can add/remove/change appointment times on their own when they want to see the doctor. Only one patient can see the doctor at a time. Each doctor using the app can have their own calendar like above, patients using the app can access any doctors calendar and can themselves schedule appointments as described above by using the app. Maybe Google Calendar can be used?? or you can make your own by extending built in android calendar class.