The above question is a pertinent one to contemplate for many companies that have neither a mobile-friendly website, nor an app.
My opinion is that aside from the hipness factor of being able to inform peers, competitors and family that you are developing an app for your business, a mobile website is a far more logical first step for most companies; particularly from a client development standpoint. That's because prospects today are seven times more likely to find a business via traditional search, than through an app search*. Sure it's possible someone can discover your app after finding your website, but isn't that process likely to occur on a mobile interface anyway?
A mobile-friendly version of your website doesn't need to replicate the breadth of the content and offerings on your traditional site, but it should present your most vital attributes efficiently. Moreover, both your mobile site and your traditional site ought to be powered by the same Content Management System (CMS) to maximize the resources you are able to direct toward the site.
Summarizing, I believe there is great potential for company (or industry) specific apps to be created over the next few years. Some will be winners and transform businesses, but I believe many will go underutilized. Before rolling those dice, establish a credible mobile website to present your company and communicate with your prospects and customers properly.
* Jason Spero, Google (Feb 2011)