Updated January, 2017

Sketch Focus is a new plugin for Sketch that boosts your productivity by keeping you on-task.

Sketch Focus offers a number of interesting workflow, checklist and annotation features: Add notes and tasks to your document,
Link layers to items, Jump directly to linked layers, Mark items as important, and more.

You can download the free version or upgrade to a paid PRO version (currently $9.99) for full feature set.