iPhone app without AppStore
Solution 1:
There are basically three different official iPhone application distribution methods that I am aware of:
- App store
With this method anyone with an iPhone can have access to the application. You can distribute an unlimited number of applications like this. Apple gets a 30% cut. Of course Apple must approve your applicaion.
- Ad hoc
You can distribute applications using ad hoc without going through the app store, but you are limited to a maximum of 100 devices. With this method you can distribute you application from a web site, email, etc.
- Enterprise
The method is for internal distribution in companies with more than 500 employees. Apple does not provide any more public detail that I could find on this method.
It doesn't sound like any of these methods meet your criteria unless you have fewer than 100 customers and don't plan to exceed that number. It sounds like from the question your customers are not internal to your company.
I would advise contacting Apple. They might be able to work out some kind of custom distribution deal.
Solution 2:
Enterprise developer program allows in house distribution, avoiding the appstore. It's $299 vs $99 and doesn't include AppStore distribution.
For companies with 500 or more employees who are creating proprietary in-house applications for iPhone and iPod touch.
Solution 3:
Apple also has a B2B Program, which sound like you are aiming for. It allows you to sell your apps directly to other businesses. You can find out more here: https://developer.apple.com/programs/volume/b2b/