This. Follow Apple's human interface guidelines and you'll get this for free. Don't treat them as sacred tomes, but it's no accident that the DPI on the iPad M

This. Follow Apple's human interface guidelines and you'll get this for free. Don't treat them as sacred tomes, but it's no accident that the DPI on the iPad Mini is the same as that of the non-retina iPhone/iPod Touch, and they suggest the same minimum tap target size on both platforms. The only exception to this is if you're making a ruler, and you're not.