Sketch 3 by BohemianCoding.com for the Mac is an excellent tool for quick prototyping designs when it comes to creating iOS screens. In this video version of my Getting Started Designing iOS Screens with Sketch 3 written tutorial I will teach you in under 10 minutes how to create and export your designs using the built in iOS template controls.
The much anticipated WatchKit arrived from Apple this week in the form of Xcode 6.2 Beta. Once downloaded and installed you can start building those watch apps! Plenty of supporting files by way of documents and video from Apple, here are all the links.