The folks at handleOpenURL.com have added support for x-callback-url to their excellent directory of iOS URL schemes. When listing your app in their directory, you can now mark whether it support x-callback-url, and we’re redirecting the “apps” page at this site to their listing of x-callback-url supporting apps.
handleOpenURL.com is a great resource, and we hope that if you have apps that use any sort of URL schemes, x-callback-url or not, you will take the time to list them.