I was digging through the Daily Exhaust archives and came across the entry in 2008 where I retired my Palm Treo 650 after getting the original iPhone.
As I mention in the post, the syncing kept me loyal to Palm. The fact that my 2008 Treo 650 identity, contacts and applications originated on a 1999 Palm Vx is kind of incredible.
Also from 2008 is my first wish for the iPhone:
I want a program that will cache my RSS feeds so I can read them offline.
One answer is that the iPhone itself is the killer application. The way Google Maps integrates with Contacts which integrates with Calendar which integrates with Mail which integrates with Photos and Camera.
The fact that I can get an email from my friend Bryan, click on his name, get taken to his contact page, select his mobile number to call him, and while I’m on the phone with him, click on his address to find out where his apartment is, and then go back to his contact page to get the URL to his site so I can read his most recent entry.
That’s the killer app for me. All of it. Together.
The other way I could answer the question is – the App Store is the killer app.
To reference my first answer above, the iPhone has solved integrated communications. Every other app is just along for the ride and will be inherently derivative, only able to tap into the various Core Services (email, browser, maps, media playback) and since the App Store is the gatekeeper to all the apps, it’s the most popular application, by design.
Now that I think about it, ‘The App Store’ is a very appropriate name, since what you’re getting with most of the apps is just that – an appetizer.
The iPhone is the whole meal.