This solved my issue with ios-sim:
git clone git://github.com/phonegap/ios-sim.git
cd ios-sim/
sudo rake install prefix=/usr/local
Got with npm install -g ios-sim following error message:
shell-init: error retrieving current directory: getcwd: cannot access parent directories: Permission denied
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rake/application.rb:50:in `pwd’: Permission denied - getcwd (Errno::EACCES)