Use "QSMS to buddy" App from android market
Use "QSMS to buddy" App from android market. This app allows you to send sms to missed/rejected calls. It also allows you to send a 'default' sms after user specified time period. e.g. you can specify to send a msg like 'sleeping at this moment' after Zero secs at night (while your phone is on silent). Watch demo at youtube with key word "QSMS : Quick SMS To Buddy Android App by Onion Systems"