Jesse dropped us a line last week over at our mondomedeusah creatrive consulting office inquiring on a solution for a vacation responder from a calendar. Have you ever been to an airport with no internet access and realize that you forgot to set your "Out of Office" (OOO) message?" You should get your calendar to automatically update your OOO message. Can this be done? But of course. With the Google Calendar API you can now retrieve calendar events and set a vacation responder for the event duration for any user in the domain using the Email Settings API.
With a little bit of coding you'll be on your way. The first thing to do is to authorize the Calendar and Email Settings client to make any call to the APIs respectively. The new Calendar API requires google-api-client library while the Email settings API still works with the gdata-client library in Python. These libraries use different underlying protocols and handle authorization quite differently.
You can download the sample code here and build your own application on top of it.