SampleSelecta is an OSX to help musicians audition, then select their favorite audio samples from a given folder. Gathering of sounds is quite a common task in pre-production; I created this app to speed up the process. Short cut keys are used to move up/down through the list, play the sample, then move the desired file to the selected area. From a tech perspective: The whole code base is in Objective-C, and uses the newer Storyboard feature present in Xcode 7.
To distribute the app I decided on using Gumroad as they take care of all payment processing, and even generate a serial key for the user. The validation of this is then done inside the app upon launch.