KiT - Keep In Touch! (Pro)

This app spares you from keeping additional handsets with you without loosing any incoming calls or sms. It forwards all the missed calls and sms that arrives on your other handsets to your dedicated email or phone number via sms.The app can be activated remotely and offers you a variety of filtering options.
It is built on Android 1.6 (Donut), so you may even make use of your old phones to keep in touch.
For bug-fixes or requesting new features, feel free to contact me.