I use Cirrus Insight.

Synching is going to be done at the data layer rather than necessarily in Skuid.  Get the Google Calendar data into Salesforce and Skuid will display it in a calendar with no problems.   A third party tool like the one Pat reccomends is most likely going to be necessary. 

Cirrus Insight is good, Ebsta is another.

Thanks guys. Has anyone used these to integrate Google Apps for an OEM product?

Just in case people end up at this thread post, there is now a tutorial for using REST to connect a Skuid Calendar component with Google Calendar. You can find the complete step-by-step instructions here: http://help.skuid.com/m/supercharge-your-ui/l/414363