Use your device while it syncs with iTunes!
Synchronicity gives you the option to use your device during an iTunes sync. Instead of being stuck at the lock screen while you transfer new content, you can unlock, run apps, make calls, etc. You can do whatever you want, except run the Music app, which is disabled during syncs to prevent data corruption.
Synchronicity works on any device with firmware 4.0 or 4.0.1.