Mark/Space recently announced the availability of The Missing Sync for iPhone 2.0, the latest version of its data-synchronization software for the iPhone and iPod Touch. It retails for $40, but it's a free upgrade for registered users of the first release.
The Missing Sync enables iPhone and iPod Touch users to synchronize Mac-based data that neither of these can devices ordinarily synchronize with, including notes, documents, and tasks. Conversely, the software also lets you log your mobile device's text messages and call history on a Mac. A "Migration Assistant" feature even allows you to transfer contacts and other data from a different smartphone to the iPhone--a boon if you're deeply invested in another mobile platform and decide to switch to iPhone.
The biggest change in The Missing Sync's 2.0 release is "true, two-way syncing of notes, tasks, and documents" between either of Apple's handheld devices and a Mac via Wi-Fi, according to Mark/Space.