Here's a quick guide for creating achieving this:
1. Install Better Touch Tool (you can download it here: http://www.boastr.net)2. Open preferences window
3. Follow the steps on the picture and paste this piece of code:
killall -s "iPhone Simulator" &> /dev/nullif [ $? -eq 0 ]; thenkillall -m -KILL "iPhone Simulator"fi
4. Press the selected keyboard shortcut and watch the iOS Simulator disappear.