iTunes Over the Air Sync

Is there any software or hack in existence that will allow iTunes to sync wirelessly with my iPhone or iPod touch? I'd like the iPhone to be constantly synced without having to plug it into the USB at my computer via the 802.11 connection, or even better I would like it to happen over 3G when I am not at home. I'd heard that is might be possible (albeit slow) but have not been able to find any software or specific steps out anywhere that lets you do it.