Publicspace has launched Rest Time for macOS. It’s a break reminder written completely in Swift and uses Apple's latest platform technologies.
Rest Time schedules breaks “intelligently,” taking into account user activity and device status. It does so without requiring privileged access, preserving your privacy and Internet security. Rest Time lives under an icon in your Mac's menu bar and pays attention to how long you’ve been working.
It requires macOS 10.11 or later. The single user version of Rest Time is available for $9.95 from the publicspace web store. The store also offers family, small business, business and enterprise licensing and customers may chose to include a "forever upgrade" with their purchase.