UC Surface was made available to the App Store on of Oct 14, 2014 (supporting iOS 7 and iOS 8) now available from the following link: UC Surface (iOS)
The alternative to UC Surface for iPad would be the versions for Mac and PC systems available on the PreSonus download page.
NOTE: UC Surface for iOS was briefly available on Oct 10th, 2014 and we immediately it pulled off the app store due to an unforeseen issue specific to iOS 8. As of the evening of October 10th, 2014, PreSonus has resolved the issue and has resubmitted the application for approval with the Apple App store. This process typically took several days to complete. We apologize for any inconvenience this may have caused.
***UPDATE: A new application was posted and is available on the following location on the App Store: UC Surface (iOS)