dontdoublebookme.com

A $20/yr service that looks at all my personal calendars and automatically throws a "busy" slot on my work calendar. Super customizable as far as what it syncs and how much of a buffer to add before and after depending on if a location is added, only during certain hours, only if marked as busy, etc. A total lifesaver and a bargain compared to reclaim.ai. I've exchanged many emails with the developer giving feedback and he's awesome.