This is implemented by the Locale Button Plug-in, which can be found on the Android Market by choosing “Get Plug-ins” from the menu of the Locale home screen.

At long last Locale 3.0 introduces the Calendar condition to detect events on your Google Calendar, Exchange Calendar, or any other calendar supported by Android.

While Locale 3.0 is available for Android 2.2 or later, the Calendar condition requires Android 4.0 or later. To learn more about Locale 3.0, please see our release notes here http://blog.twofortyfouram.com/post/19303488607/locale-3-0