On a web page that is to be displayed on an iPhone, is there a way to get the number pad to come up when the user taps in the field, instead of the qwerty keypad?
This guy says here's how to do it, but as of 2.0, this "feature" was disabled.
I'm guessing there's some fancy javascript to employ to get around this limitation?
Yes, this used to be possible by including the word "zip" in your text field's name attribute. Unfortunately, Apple seems to have removed this in 2.0 and later. I suggest you file a bug.
You can make calls from JavaScript to Objective-C and then display what ever you want. If you want a framework to help you out you could check out QuickConnectiPhone. It is available at https://sourceforge.net/projects/quickconnect/.
You could also check out http://tetontech.wordpress.com. This is the develpment blog for QuickConnect. It has some example code in addition to that which is included in the sourceforge download.