In his opening keynote speech at Google Developer Day this morning, Google Engineering Vice President Jeff Huber called out Spanning Sync as an example of the kind of innovation being built by third-party developers in the Google ecosystem:
Another great example is Spanning Sync. Google Calendar has been an enormously popular product we introduced about a year ago. With the GData API, Spanning Sync is able to create a syncing mechanism to make it work with iCal and iSync on the Mac. So you can now sync your calendars to not only iCal, but to mobile devices, to your iPod, etc.
The day's sessions are being webcast, and will be uploaded for later viewing once the event concludes this evening.