Another way to install this on OSX if you use Homebrew package manager.
1. Install Homebrew if you don't have it already
http://mxcl.github.com/homebrew/
2. Install the brew-pip package
brew install brew-pip
3. Add Homebrew's pip path to your PYTHONPATH environment variable (you probably should add this to some sort of shell initialization file like ~/.bashrc or ~/.zshrc)
I got this working by just installing pip and then entering "sudo pip install glances".
I have to say, I think this will replace htop for me on my mac. It's actually more useful than Activity Monitor is since it also shows network interfaces.