Just found another cool tweak for the 4S that works awesome with the AppRadio. It's called Hands-Free Control. It allows you to activate Siri without touching your phone. All you have to say is "Siri, launch Pandora" and the app launches and starts playing. I've read some complaints that it causes problems with making phone calls, but if you don't use the phone feature of the AppRadio (or can't because the microphone sucks), it's a great addon.
Edit:
Forgot to mention that I use Activator to enable it when the phone is plugged in and disable it when unplugged. Really helps with battery life/accidental triggers when not in the car.