Microsoft at the Dev Sumit said that Windows Phone 8 would have Lense functionality that would extent what the built-in camera would be able to do. As a part of the Windows Phone 8 SDK leak, more have been revealed about what that is. Developers will be able to plug-in their 3rd party apps which can be accessed within the default UI.
In Windows Phone SDK 8.0 Developer Preview, you can create a lens that appears in the Windows Phone built-in camera app. A lens provides the user a consistent entry point into the viewfinder of your app. It is a type of extensibility available to apps that provide unique camera functionality via the camera APIs. As a lens, your app provides the user with a viewfinder experience and interacts with the camera directly. For example, a bar code reader lens would present a viewfinder to display the bar code that it’s going to scan.
Lenses shown in the lens picker also are listed in Marketplace in their standard app categories. Although a lens must provide a viewfinder experience when launched from the lens button, the app can provide other experiences, too. For example, you might create a productivity app that displays a panorama control when a user starts it from the App list. But when a user starts the app from the lens picker, it displays a viewfinder.
When a user taps a lens in the lens picker, the corresponding app is launched via a deep link URI. The deep link URI targets the corresponding app and includes the string ViewfinderLaunch to indicate that the app is to be launched as a lens. Apps can use the deep link URI to recognize a lens launch.
After opening a lens, the user can tap the hardware Back button to return to the built-in Camera app.
This enhanced camera functionality should bring a lot more camera apps to Windows Phone. Maybe we will get lucky and see Instagram one day.