Update: This app seems to break core functionality, read my article here on uninstalling Wi-Fi Sync. Until the developer decides these issues need to be addressed, I can't recommend anyone pay for this application, or until another workaround is found. The developer has been completely unresponsive when I've tried to contact him about the issue and at this time, I have no current easy solution to resolving broken backups and upgrades.
Wi-Fi Sync for iPhone is a jailbreak app that allows you to wirelessly sync with iTunes as opposed to having to plug in your phone. It found it's way into Cydia after it was rejected by Apple.
As of now, Wi-Fi Sync is only Mac compatible. The developer is currently working on a PC version which he states on his website should be complete in about 8-10 weeks. If you have a Mac and want to try it out, simply click here to get the Mac desktop software, then go in Cydia and purchase Wi-Fi Sync [$9.99 - Cydia Link].
After you've installed Wi-Fi Sync on your Mac and your iPhone, you should now be able to pair them. The first time you do this, you'll need to be by your Mac as it'll ask you to accept the connection. You'll see this new icon in your Mac task bar (far left).
From that menu you have a few settings. One being to disable backups. I did this, as backups typically take a while and obviously, over wifi, your syncs will not be as quick as they are via traditional USB connection. It'll definitely make your battery take a hit with backups enabled as the time it takes to sync drastically increases. To disable backups, just click that little icon and click to disable backups.
Now I don't know if it was just me or if it's a bug but my Mac kept asking me to accept the connection everytime, or wouldn't find it sporadically. There was also a couple times it would boot me off and my iPhone would tell me I had no wi-fi connection. As this app is in it's newborn stages, we will see how it progresses in terms of stability and feature set. As far as I see, you'll also need to tell your phone to sync automatically if you plan on using this app while not directly in front of your computer. If that setting isn't there, you'll physically have to be in front of your computer to hit sync, which to me is somewhat counter-productive.
In my opinion, it's a nice tool but I don't know if it's worth $10 at this point. I personally encountered a few more bugs than I would have expected for an app with this type of price tag. We'll see what the developer does to refine it in the coming months.