Question

How can I find out what notifications the iPhone has registered?

for instance:

notify_post("com.apple.springboard/Prefs");

Answer 1

Although an answer has already been confirmed for this question, since @Nate seemed confused about it, I thought I’d show an easier method.
notificationWatcher from Erica Utilities can be used to print a list of standard notifications as they happen. Run it from the command line like so:

notificationWatcher -st | grep -v rawOrientation

You don’t need the grep bit, but it’s useful to remove the many com.apple.springboard.rawOrientation notifications that appear when the device is moving around a lot.