This is very useful item in everybody's day to day life.
With google calendar you can
1) Schedule your day to day calendar
2) Access online from anywhere
3) Get Free email reminders
4) Get Free SMS reminder
see the Website Development Blog
For SMS reminder you need to setup your mobile number and get it verified. You can select your preference for getting reminder over either email or sms and minutes / hour earlier to the event.
This is very useful tool and no doubt that it will be a big go ahead for google as most of the its millions of users will love using it for free and very easily.
To know more click here http://www.google.com/calendar/
