Much has been made lately about iOS 4 (what used to be known as the iPhone OS) and its ability to “multitask.” This is typical Apple obfuscation, however, because for most the iPhone won’t be multitasking in the classic sense. As The Unofficial Apple Weblog (TUAW) puts it:
With the upcoming iOS 4, Apple has announced a solution for some of those applications, but only a handful of specific kinds of applications: location data, voice over IP (VoIP), and audio. You will be able to stay on a Skype call even if Skype is in the background, once Skype adds support for it. You will be able to listen to Pandora Radio in the background once Pandora adds support for it. Your GPS app or other location-aware app will be able to keep tabs on your location in the background, once it is updated. In fact, Tom Tom has already announced that its navigation app will be background-ready, so your "At the end of the road, turn left" announcements will come through even if you’re doing something else.
That’s it, though. Background processing is extremely constrained to three specific areas, which Apple believes will cover most of the things that most people want to do most of the time.
Since what iOS 4 is offering is not really unfettered multitasking, Instapaper can’t program itself to automatically update itself every X hours or minutes. Neither can your RSS reader. Neither can Simplenote. Neither can 1Password. Neither can TextExpander. Neither can any other application.
This last paragraph is the most important. In short, what Apple is providing is a set of background services that an application can tap into. What webOS provides, however, is the sort of “unfettered multitasking” that TUAW talks about here. In short, an application like the Feeds RSS reader can run in the background to update feeds, as can Twitter apps and any other app that can benefit from running background tasks outside of the specific areas allowed for by Apple.