It's the Smooth Reflections app. I have not tried the Sky HDR app. The Smooth Reflections app simulates long exposure by taking 64 to 256 shots and combines them in the camera. Only negative I can think of is wear and tear on the shutter.
One more reason to use an ND in conjunction. Looks like it works great for ultra wide angles without ND. The raw is amazing, $5 for the app is a bargain for landscape lovers.







