What does it take to build a company these days? How about some free Google software, a piece of cardboard, and some ingenuity?

At their annual techfest held in San Francisco this week called Google I/O, the biggest company in search announced updates to the most ambitiously low-budget project ever invented. You rip off a piece from a box and download some instructions. Then, you grab some some code and build an app. It helps if you can also make some virtual reality video, and GoPro has a new 16-camera camera ring to help.

The result is an app that can transport the viewer to another world -- sometimes literally (if it's a science fiction game). An app might show you ocean where you can reach out and "touch" a dolphin or swim around a coral reef. When you move your head, you look around the VR realm (up, down, and side-to-side). The Cardboard kit involves slipping an Android phone or the iPhone into a holder. That's it.

OK, what the heck is going on here?

According to KZER Worldwide, the virtual reality industry will grow to a whopping $5.2B value by 2018. Google has some competition in the space, including a pair of goggles I tested recently from Samsung, a new one from HTC, and the Oculus Rift.

However, the ingenuity behind the Cardboard project, which Google is emphasizing even more after announcing it a year ago, is astounding to me. Anyone can make an app, anyone can make the goggles, anyone can create the content. I haven't seen a market for new app development that looks this promising since the early days of the Android smartphone. It's really a gift to anyone struggling to figure out which emerging market could be the one that takes them from rags to riches.

It has all the hallmarks of a major ground-floor trend. First, it's highly visual, so people want to try it just to get some easy bragging rights. (When I had the Samsung goggles for a week, I showed them to everyone I know and even a few strangers.) It's brand new and innovative. Second, this is Google. The company is known for making experimental products that are a little unobtainable or obscure, but this is a product you make out of cardboard (you can also purchase it for about $25).

There's also a low-cost, visually engaging, and well-supported product-meets-software angle here. It's a perfect marriage: a free product with endless app potential. It's like the razor is free and so are the razor blades.

Already, I'm seeing the potential for any new business (and maybe a few old ones) to get in on the act. What to do? Where to start? Get people into your retail store virtually. Develop a game that's free to try. Give people a virtual reality tour of a remote area. Invent a new form of videoconferencing. Create a platform for doing job interviews in a virtual reality setting. Make an app that helps you sleep.

The only real challenge for making a cardboard app is that, if you do want to make virtual reality video, the costs can be a bit high. Fortunately, if you use the GoPro Jump camera system, Google even provides the video stitching software you need to create the video.

Small-business idea? Game-changer? Money-making opportunity? Yes, yes, and yes.