Which Apps are threatened by Apple's upgrades?

How do you know if you've created a really great, useful iPhone app? Apple tries to put you out of business.

That may be overstating it, but a number of new features for Apple's operating systems that it announced at its Worldwide Developers Conference have been available through existing apps and services for some time. Some of those apps are quite popular, and have been lucrative for the people who developed them. Here's a quick rundown of some of the services and applications that will be living in a changed world thanks to Apple's new operating systems for Macs and iPhones:

Instapaper: Safari's new Read Later feature allows you to access Web pages that you have saved for later across multiple iOS devices. You know, like Instapaper.

Readability: The new Reader mode in Apple's Safari browser strips down online articles to images and a rolling column of text. Readability basically did the same thing.

Boxcar: This nifty app lets people manage their notifications in a single place, instead of having them pop up on their iPhone's screen willy-nilly. The new Notifications panel in iOS 5.0 centralizes notifications in the same way.

To-do apps like Remember the Milk: Apple's new Reminders feature can alert you to do something you've written down either based on time or location (pass by a grocery store you've marked in the app and you will be reminded to, um, remember the milk).

Camera+, QuickPix: One of the complaints about the iPhone's camera is that it can take a while to get to when you want to take a picture in a hurry. Some apps used their faster start-up time as a selling point. The upgrade to the iPhone's software includes the ability to place a camera button on the lock screen, for quick access. Users can also use a volume button as a shutter release, something Apple denied an app, Camera+, in December 2010.

Photo editing tools: While the popular filters of Hipstamatic and OldCamera do not seem to be in jeopardy, new features in the Photo app include cropping, red-eye reduction and one-touch auto-enhance, which may be enough for some picture takers.

Dropbox and other cloud storage services: iCloud, Apple's free solution for storing documents and photographs in the cloud, may eradicate the need for independent services that let users do the same thing.

GroupMe and other messaging apps: iMessage will let Apple customers send messages to groups of friends -- something that start-ups like GroupMe, Kik, TextPlus, FastSociety, Pinger and their ilk have been doing for months.

Apple clearly values their developers. They are a source of innovation and development. The company was proud to announce during the keynote that it had paid out more than $2.5 billion to developers. But there is another message to developers too: If you are really good at what you do, you will be assimilated.