Have you got itunes beta? In the options in itunes it says "sync over wifi". You have to check that box. Once you have done that go into your iphone>>settings>>general and click on itunes sync then you press sync now!
Install iOS 5 beta 2 on your iOS device.
Install iTunes 10.5 beta on your computer.
Plug your device into your computer and open iTunes.
In iTunes under the summary tab for your device, enable “Sync over Wi-Fi connection” and sync your device via the usb connection.
Untether your device from USB, and your device will still be recognized by iTunes!
Drag and drop files from iTunes to your device, and WATCH the Wi-Fi Sync work
You access the wireless sync from the idevice in settings>>general>>itunes sync. Your Itunes must be open for it to work!