BitWiz is great. It’s the kind of app that iOS is made for in my view. I love how easy it is to generate a patch randomly and then play with the parameters without too much knowledge of how it works even.
It has great sharing facilities and I especially love the visualisation. It’s a winner. If you like noise makers, simple code and generating things on the fly to be awed by how much fun simple synthesis can be, then you should get yourself a copy.