Building a device for single users, not app store

Hey guys, I am working on an App for IOS that is a utility type app that a business has hired me to create. This is an app that the owner of the business will be using, but no one else. Because of this, I don’t want to have to put the app onto the App Store because its intended to only be used by this one person. What options do I have for getting this app installed on the owners IOS devices? All I can think to do is get his device UDID and add it to my developer account as a testing device so he can run a developer build of the app. Any thoughts are appreciated, thanks!