For iphone prior to 5, I used "iOS-Simulator Cropper" (http://www.curioustimes.de/iphonesimulatorcropper) which was used to quickly create images of the device, containing the image taken by the simulator. Unfortunately it was not the most updated... you know something like that, also compatible with the new devices iPhone6/Plus?
iTunes Connect will not allow you to upload images that are the incorrect size. If you are concerned about the status bar detracting from your images you could use Simulator Status Magic (https://github.com/shinydevelopment/SimulatorStatusMagic) This will modify the simulator to show:
9:41 AM is displayed for the time.
The battery is full and shows 100%.
On iPhone: The carrier text is removed, 5 bars of cellular signal and full WiFi bars are displayed.
On iPad: The carrier text is set to "iPad" and full WiFi bars are displayed.
To save the screen shots you can just press cmd + s or click File > Save Screen Shot.