They have released iOS only apps before (see the Gboard), but specific to this one, it works with iPhone 6's live photo feature. This is where the phone records

They have released iOS only apps before (see the Gboard), but specific to this one, it works with iPhone 6's live photo feature. This is where the phone records a three second movie clip starting 1.5 seconds before and ending 1.5 seconds after you press the shutter button. It makes sense that this would be an iOS only app given that most Android's don't have a live photo feature.