To answer your question.. yes.. I want SMS autoforwarding. I would also like 'missed call' autoforwarding. I do not want to forward SMS messages internationally, as that would ring up a huge cost for me (live in Australia), and I'm not setting up google voice.
In essence, I want to plug my current sim card into my spare android phone, have it left on and wifi connected.
All calls go to that phone, all messages go to that phone.
All txt messages then go autoforward to my phone overseas, and would appear in the starndard android sms apps as if they were sent directly to my phone. That way, I can use internet txt messaging apps that 'spoof' my number as if its coming from my normal phone number.
All missed calls would appear on my overseas phone as missed calls in the standand android phone log.
Integrating with dropbox would be great. And yes, this would require a client/server model (really just have the 1 app and have an option in the app to be the client or server).