A Shiny Gadget is an interactive tool that enhances your R programming experience. You make Shiny Gadgets with the same package that you use to make Shiny Apps, but you use Gadgets in a very different way.
Where Shiny Apps are designed to communicate results to an end user, Gadgets are designed to generate results for an R user. Each Shiny Gadget returns a value that you can immediately use in your code. You use Shiny Gadgets during the course of your analysis to quickly hone iterative tasks in an interactive fashion. For example, you might use a Shiny Gadget to preview the matches that are generated by a regular expression–as you write the expression. Or you might use a Shiny Gadget to identify high leverage points in your model–as you fit the model. Unlike Shiny Apps, Shiny Gadgets do not need to be deployed on a server. Shiny Gadgets are defined right inside of a regular R function. This is important, because it means that Gadgets can directly access the function’s arguments, and the return value of the Gadget can be the return value for the function. Despite this difference, almost everything you know about Shiny Apps will transfer over to writing Shiny Gadgets.