Apps, websites and other services you've connected with via the new Google+ Sign-In button will be displayed on your profile.
Apps connected to your account will display under "Links" on your profile
But before you start worrying that everyone will be able to see the list of apps installed, Google is already one step ahead, providing advanced privacy settings for the feature.
When editing your profile, just click on apps to toggle whether you'd like them displayed on your profile or not, if you do want them shown but only to select people or circles, you can always change this in your app settings.
The app settings box
The launch partners for the Google+ Sign-In feature are:
Developers are welcome to add Google+ integration to their apps and websites. To find out more information, +Google+ Developers has everything you need to know here.