Mobile Secretary is a freeware application for Windows Mobile 5.0 PPC that allows your mobile device to automatically respond to a missed call with a custom text message and optionally with your current calendar information instead of just letting them hear your voicemail and wait for you to respond. You can customize the messages for various groups of people as well. And also forward text SMS messages to another cell phone.

Download Link- http://blogs.msdn.com/windowsmobile/attachment/862241.ashx via Windows Mobile Blog