As an iOS developer that sells an app based on a subscription model, everything he said is right. Subscription models work, and if you take a real hard look at it, from a consumers point of view, especially that we are using a very niche product and a not-very-inexpensive system to implement, the cost isn't that big of a deal. If you amortize it, verses how often you use it, $50 bucks a year isn't bad at all.
Now, if Danny could figure out a way to license the app, and possibly customize graphics for all of the installers out there that want their customers to use it (and sell it as an add on), then that's a possible additional income stream for both him, as well as the installers (who could get a cut, too). Wouldn't that be cool if the installer got a monthly royalty out of the subscription model, too?