DataSync is, as the name suggests, and application to help you sync your data. It can sync directly peer-to-peer via WiFi or, more usefully, via a cloud storage service such as Dropbox or Box (I use Dropbox personally). Up until now the process has needed to be manually started or scheduled, but now, thanks to a new Beta version of the application, the sync process can automatically happen on application launch or exit - amazing!
How well does it work? Fantastically well. I'm using it between a number of devices and it's fantastic, even in it's Beta phase. Not too long ago DataSync's UI, while looking quite good, didn't really work that well but I'm pleased to say it's really come on in leaps and bounds and it really is one of my must have apps now.
In order to try the 'real time sync' functionality you need to install both the 'DataSync Beta' (free) and the 'DataSync+' premium key (£1.59).
Let me know if you give it a try and how you get on!
[Edit: Note that root access is required!]
Click here to view the item