This is a feature from Google calendar I was waiting for. Over the last year, I transferred my planning from my old fashioned calendar system to Google Calendar. I get my reminders sent to my cellphone via sms, receive confirmations of appointments... I can share my calendar with my wife or friends and can limit, what they can see. Google Calendar is linked to Gmail and emails with appointment requests are transferred automatically to the calendar. It is one of the things, I don't want to miss. What I was missing though, was solution for my cellphone, when I am out the office and want to make new appointments or check my availabilty for the next couple of days. Finally, Google produced a solution for my need.
If your mobile phone has the capacity to access the internet, you can log into your Google calendar by going to http://calendar.google.com. I got used to check my emails on the go and being able to check my calendar the same way is exciting. The capacities of the new feature are limited though. You can quick add new events, which is great, but you can't edit or delete current appointments. If you need a quick overview over your schedule for the next couple of days or enter quickly a new appointment into you calendar it is a useful tool. I assume that Google will upgrade the application in the future.
Check out the announcement from Google's blog.