CalenGoo is a very flexible and feature-rich calendar app

Add-On to send SMS message to customers

This is a 5 day trial version of the CalenGoo Calendars and Tasks app.

Syncs one calendar into another, e.g. from Exchange to Google Calendar

Dialer add-on for CalenGoo to dial special phone numbers with extensions

Paid subscription service for public calendars (holidays, sports, TV and others)