Awesome app for previewing app icons directly on your device. Easy, seamless integration with your Mac: drag and drop an image to the menubar icon, and, bam, it's on the device. The Mac companion app is free and can be found on the Mac App Store here.
The only caveat is that you can only preview one icon at a time. I ==really== hope they will add the possibility to add several icons (grid or even scroll based) so you can be able to compare several iterations at once.