We use BusySync just for our family to make sure we have a up-to-date family calendar between us. With the new 2.0-Beta it also syncs perfectly well with Google Calendar, which in turn can fire off SMS’es as reminders!
Sync iCal with Google Calendar
BusySync 2.0 synchronizes iCal with Google Calendar, enabling you to:
View and edit calendars online — Calendar events can be created/edited in both iCal and Google Calendar and automatically synchronized between the two.
Sync calendars between home and work — Users can sync their home and office computers with Google Calendar (as an alternative to syncing calendars with .Mac).
Share calendars remotely — Users in remote locations can share calendars with each other by syncing shared calendars with Google Calendar, even while traveling.
[From BusySync 2.0 Public Beta]