It shouldn’t come as a surprise that offline web apps are on the way to iPhone and Android platforms in the form of Google Offline. The trick is that newer browser technology allows the storage of cached information in database form. In Firefox and Safari, you currently need Google Gears to do this. Soon it will be built in (like in Chrome).
Also, new betas of Firefox allow geolocation in the browser but as you can see from the video below, so do new versions of Webkit. This should be standard in all browsers within a year. The video from MWC 2009:
And also a Palm Pre running Google Maps as a web app, below