"I've got a great idea for an app." It's probably the single most common statement of intent from would-be digital entrepreneurs. But how realistic is it to build a company based solely on an app?
Looked at one way, it's a challenging environment. Forget about Candy Crush and Angry Birds: at least 90pc of published apps make little or no money, with most never getting a developer update.
But there are some real success stories, too. One of Apple's most celebrated app-based startups is actually a Dublin-based company that has dominated its category for years.
3D4Medical's 3D anatomy apps have generated sales of $20m in the three years they've been in app stores. And there's no sign of any slowdown.
"We've had a very good week," says John Moore, founder and chief executive of the Ballsbridge-based startup which now employs 35 people and looks set to hire another 30. "In fact, it's been one of our best ever weeks. We've been number two in our overall category, not just the medical one. That's 150,000 paid sales in the last five days."
Overall, 3D4Medical has seen a staggering 9m app downloads in its short history. But while it is a standout in the app economy here, it's by no means the only local business profiting.
Apple, which still dominates app-based commerce, says that there are 4,000 members of its paid developer programme in Ireland. At a wider European level, the company claims that its iOS ecosystem is responsible for over 530,000 jobs (including 300,000 paid developer programme members) and that €6.6bn has been earned from Apple App Store sales.
In 3D4Medical's case, the platform suits the business perfectly.
"There is no barrier here for us," says Moore. "When we started out we were a very small company with no money for a salesforce or a marketing team to give us visibility to hospitals, doctors or universities. We had to rely on organic growth. So the App Store became a very unique ecosystem for us. It allowed us and other smaller companies to concentrate on what we were good at, while giving us the chance of visibility to more than 300m iOS users around the world. That was huge for us, like having a shop front window in every high street in the world without having to put the money into such promotion."
It helped that Apple like 3D4Medical a lot. The company's apps have regularly been placed into prominence by Apple's App Store curators. On the other hand, you quickly fall off the radar if your app isn't any good.
"The beautiful thing, as well as the horrible thing, about the App Store is that it is a very open system," says Moore. "You live and die by the reviews you get. So if you're not medically accurate, you'll get crappy reviews very quickly and won't be in the charts very long. Every day we get thousands of emails from specialists in different areas that might be of concern. We also have a very good relationship with Stanford University and that gives us a nice stamp."
Google also has a substantial app ecosystem in its Play store, but companies like 3D4Medical say that the bulk of their income comes from Apple's App Store.
"Even though we have apps on all platforms, I can tell you that the App Store produces around eight to one in revenue compared to Google," says Moore. "We have found that people on the Play Store expect the apps to be free or a dollar, while on iOS they don't mind paying more. Some of our apps cost $99 and they still sell well."
The company has big plans for the future.
"We're only at the tip of the iceberg," says Moore. "Medical textbooks are an $8.5bn industry and we are starting to dig into the traditional book publishers, many of whose mobile strategy was to take books of 70 years and make PDFs out of them. And that was never really a great experience. So we're planning a new suite of products which will be 20 times better than what we already have. It's a big area, with doctors, chiropractors, paramedics and nurses. There are 4.1m nurses in the US alone."
The impetus behind this partially lies with a shift in legislation from the US.
"There are massive changes going on within hospitals with physicians and how they consult," says Moore. "New laws will say that if you go to a consultant, he must make a medical record and store it. There are a lot of things attached to that, to educate the user. Because of that legislation and because our stuff is digitised, it's a natural progression that the consultant uses an app and backs it up into an electronic medical record."