The International Motor Sports Association (IMSA) has released an official app for both Windows 8.1 and Windows Phone today that brings streaming video, radio, and live timing and scoring from several racing events right to your Windows device.
The IMSA app was developed in partnership with Microsoft, and brings live race coverage from official IMSA-sanctioned events such as the TUDOR Championship, Continental Tire Challenge, Porsche GT3 Cup Challenge USA, Lamborghini Super Trofeo, and Cooper Tires Prototype Lites.
Within the app, all of the above races will be tracked with live timing and scoring coverage. Users can also register for what IMSA calls a "free premium experience" that brings streaming IMSA radio audio for each race, along with streaming video for all of the above events except Cooper Tires Prototype Lites. If you're interested in checking out tons of race coverage from your Windows device, you can download the free apps from the store links below to get started.
Source: IMSA (Thanks to Richard for the tip!)