PageOnce, a startup that wants users to access all their web accounts through a single site, is now bringing its service to the BlackBerry. The company’s free mobile application has already found some success on the iPhone, and chief executive Guy Goldstein says smartphones have become his focus.

“This is our business now,” he says.

Back in June, Palo Alto, Calif.-based PageOnce launched as your standard web-based business, and I was already impressed by the concept. It allows you to access your Gmail, Amazon and Facebook accounts, as well as many more, from a single page. The most popular component involves bringing all your financial information together, so you can almost think of PageOnce as a version of financial supersite Mint that doesn’t focus exclusively on money. Goldstein says the standard site is still up and running — after all, it’s still easiest to set up and add accounts using your computer — but the mobile side brings out a lot of Pageonce’s utility. For example, if you just have a few minutes to kill while you wait in line at Starbucks, you can whip out your phone and immediately bring up an overview of your finances.

The free iPhone application has been downloaded 200,000 times, Goldstein says, and the BlackBerry app should achieve similar popularity, since it’s a logical fit with the business-oriented smartphone. PageOnce’s business model is based mainly on advertising (Goldstein says the company may charge for the BlackBerry app when it leaves beta testing), and of course that’s a bit risky as the economy slows down. But PageOnce may be able to weather the storm better than most, since the ads are targeted, and can also be tailored to the smartphones’ features. Usage, meanwhile, has actually gone up during the current financial crisis, with people becoming more anxious to track their plummeting portfolios.

Goldstein gave me a quick demo of the iPhone and BlackBerry apps last week. They have virtually all the functionality of the normal PageOnce website, and appear well-designed, so you can get a quick overview of your accounts, then drill down with ease. Putting this much power into your smartphone also presents some security risks, but PageOnce has taken steps to avoid trouble. For example, if you lose your phone, tell PageOnce and the company will make the app “self-destruct” on your device.