SIM Switcher is a small utility that will allow you to choose which SIM you want to send your outgoing SMS from if you are using the threaded mode for your inbox.
How to: 1. Map it to a hardware key ( i am using the record button ) 2. After typing your outgoing sms, execute the application by pressing the mapped hardware key 3. A Yes/No dialog box will popup. Choose YES for SIM1, NO for SIM2 4. Press SEND 5. That's it.