New Core Feature: Async Framework (Master Branch and 4.8)

Unless I misunderstand, you should be able to accomplish what you want with the regular FAsyncTask.

Check out the code for sound decompression, it can be used in a similar manner https://github.com/EpicGames/UnrealEngine/blob/311e18ff369078e192a83f27834b45bdb288168a/Engine/Source/Runtime/Engine/Public/AudioDecompress.h