Recently I've released a slow-mo app Sport Camera. Unfortunately it is not a "true" slow-mo. But I will update the app as soon as devices supporting @60 fps appear.
I don't think app could do this :/ as far as im aware you camera would need to be able to film at a higher frame rate e.g. 60fps or 120fps to get 'true slow motion'. you can slow the movie down in post but it would become nasty to watch. its just a limitation of hardware. unless someone brings out a camera with slow motion capable camera (iPhone 5s) I don't think we will be getting slow motion on windows phone, sorry![]()