When it comes to new ventures, the advice to avoid "diving into a crowded pool" is sound. The problem? It's not always enough to just recognize a need and create a new product or service that fills a vacuum. Even if you're operating within a niche, you still need to be innovative.

But bringing innovation to large, crowded markets can be incredibly difficult. True, creating the next iPhone or Facebook has the potential for a huge payoff, but that doesn't mean that going mainstream is a surefire path to success. Often, it's more worthwhile to focus on a specific, if smaller, market. These four companies are great examples of going niche without sacrificing innovation:

Square replaced clunky old registers with free, powerful POS software that stores data online but also works offline. It used to be that business owners and entrepreneurs could only accept credit cards if they had a proper store with a cumbersome device with which they could swipe cards; Square changed all of that.

And with Square Register, a free app that turns a phone or tablet into a point of sale and control center for one's business, Square brought real innovation to the market with its ultra-mobile card reader that anyone could plug into their iPhone.

TravelersBox enables travelers to deposit coins and bills into their TravelersBox stations situated in airports around the world. No longer do travelers need to worry about emptying countless coins out of their pocket at every security check, or arriving home with various foreign currency. Travelers can drop leftover foreign currency in their ATM-like box and receive either a deposit directly to a PayPal account, gift cards, or just make a donation.

BlueVine helps small business owners streamline their cash flow. The service helps free up the cash trapped in invoices by giving an advance on the amount due. There is no paperwork, no obligation, and no hidden fees. With BlueVine, small business owners can access the capital they need, when they need it.

OpenLegacy addresses a very specific problem, enabling enterprises to quickly and rapidly extend and transform legacy systems such as the IBM i and mainframes to the web, mobile, and cloud.

"OpenLegacy grew from the frustration of trying to solve a countless number of legacy modernization business problems with the tools at hand; tools that solved a technical problem but not necessarily the fundamental business problem," said Romi Stein, CEO of OpenLegacy. "A different and new approach was necessary, a solution that looked at the problem from an end-user/business owner perspective. A solution that was quick to use, easy to learn, and flexible in its usage."

A standards-based open-source development platform, OpenLegacy lets developers solve high impact business problems quickly, giving enterprises new-found agility and opening the door to creative new solutions at a low cost and with a high success rate.

As Square, TravelersBox, BlueVine, and OpenLegacy have proven, focusing on a niche and innovating within it can be the key to success. "Innovation distinguishes between a leader and a follower," the late Steve Jobs said. "It's not about money. It's about the people you have, how you're led, and how much you get it."