SyncThemCalendars is described as 'allows you to block time in one calendar based on events in another calendar' and is an app in the Office & Productivity category. There are five alternatives to SyncThemCalendars for Windows, iPhone, iPad, SaaS and Mac. The best alternative is Outlook Google Calendar Sync, which is both free and Open Source. Other great apps like SyncThemCalendars are gSyncit (Paid), OggSync (Paid), Spanning Sync (Paid) and SyncGene (Paid).
Spanning Sync 3 is the one app that syncs both iCal with Google Calendar and Address Book with Google Contacts. It gives you even better control over how your information syncs, and is now up to 10x faster!