Microsoft has had several years to refine their speech recognition technology, and it's about time for them to open some of that tech up to help developers interface with that. Microsoft is releasing the Custom Speech Service today as part of an ongoing effort to make several Cognitive Services tools available to developers.
— Microsoft Research (@MSFTResearch) February 7, 2017
The Custom Speech Service is a pretty big asset for developers who intend to open up speech recognition features in their apps. For instance, it lets developers specifically tune their app's speech recognition to match the dialect of the people it's aimed at. It also lets you design your own acoustic environments, so you can account for the background noise that you expect your users to be around while they use your app.
This is just the beginning for developers looking to get cognitive services going in their applications. Content Moderator and Bing Speech API are both coming along in March, and you can expect all of the other API's to make their way to you some time soon.