PixelLove is offering icons for use with your iOS designs. They have a Pro version and a lite version called the Infinity pack.
700+ iOS 8 tab bar icons & toolbar icons, retina ready with vectors & strokes for easy editing. Web fonts and free updates also included as part of the 'Infinity' pack.
In addition to the paid sets they have a royalty free set of icons available here.
These icons are great for use in Sketch 3.