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].