I've been corresponding with some of the folks over at AgileWebSolutions and I am really excited about the public beta of their latest version of 1Passwd (version 2.5) They've added a function that allows you to create a password protected bookmarklet that contains all of your secure 1Passwd data. It then syncs into mobile safari as a bookmark. When you click it you get a screen that looks something like this.
Once you put your password in you get access to all of your 1Passwd data in your pocket.
This is huge for me. On my Treo I used a program called SplashID to keep important data in my pocket. 1Passwd figured a way to do this on the iPhone.
There are some limitations. It doesn't take the data and "go and fill". For instance if you click on a password in the bookmarklet, it doesn't open the web site and fill it in for you. Also you can not edit the data on the phone. The developers are working on the "go and fill" feature. The text also isn't always formatted perfectly and sometimes it runs lines together.
Regardless, this is extremely useful. I have all my insurance/medical/financial data available to me and still securely locked down. It doesn't rely on any hacks and, since it is Safari, you can even flip your phone on its side to make the data larger.