Complex activities often require people to work across multiple software applications. However, people frequently lack valuable knowledge about at least one application, especially as software changes and new software emerges. Existing help systems either lack contextual knowledge or are tightly-knit into a single application. We introduce an application-independent approach for contextually presenting video learning resources and demonstrate it through the RePlay system. RePlay uses accessibility APIs to gather context about the user's activity. It leverages an existing search engine to present relevant videos and highlights key segments within them using video captions. We report on a week-long field study (n=7) and a lab study (n=24) showing that contextual assistance helps people spend less time away from their task than web video search and replaces current video navigation strategies. Our findings highlight challenges with representing and using context across applications.