WatchSim is a $9.99 utility (paired with free Mac server tool) that sends a live preview of your currently running Watch Simulator to your iPhone. On your iPhone it is displayed at actual size. But most importantly, the iPhone projection is interactive. The touches, swipes and presses you do on your iPhone are sent back to your Mac in realtime.
Obviously once April 24 arrives and we can run on actual hardware this will won’t be quite as necessarily. But until then this tool will be the perfect aide in polishing up my apps.