That app is Vudu. Remarkably, Vudu is the only service offering the flagship streaming formats for video and audio: Dolby Vision HDR and Dolby Atmos surround. However, no current streaming box/stick sports Vudu with both Dolby Vision and Dolby Atmos. The only way to get it all is with Vudu built into flagship-level Smart TVs such as recent LG OLED TVs.
Honorable mention: Apple TV 4K’s Movies app. Apple Movies is the only other streaming service offering Dolby Vision, so at least you can get the best possible streaming picture. Apple Movies also gets kudos for lowering the average price of 4K streaming movie rentals from $9.99 to $5.99—the same as 1080p rentals. (Vudu quickly followed suit.) However, the app falters in sound, with no Dolby Atmos — merely different flavors of Dolby Digital.