Sketch resource rebound off of Pixelautomatic's iPhone 5 Wireframe template here: http://pixelautomatic.com/2013/11/07/this-morning-i-created-a-super-simple-wireframing/
The canvases are separate from the device outlines for easy export, so you can use something like Flinto to make a fast, realistic app that your users can test on :)