Today’s best smartphones are really hand-held computers. They run a vast variety of applications, from productivity programs to games, that mimic what laptops do. Their biggest limitations for serious work, gaming, Web surfing and multimedia are their small screens, cramped keyboards and tinny speakers.

developed touch-screen technology that promises to improve sensitivity of touch screens while improving battery life and screen resolution. It seems like a perfect candidate to thrive in the new market for mobile devices, but the emergence of that market may have cost the hp dv6700 battery company its opportunity.

After spending 18 months verifying that RPO’s technology worked, a major Korean laptop company was planning to begin manufacturing a notebook computer with a touch-screen using RPO’s components. As recently as December, the Fremont, Calif.-based company was turning away potential customers in order to be able to fulfill its commitment to the notebook maker, said RPO’s former chief executive and chairman, Malcolm Thompson. He declined to name the Korean company.

But in January, the  hp pavilion dv6500 battery manufacturer, “backed out, rather surprisingly, at the last minute,” Thompson said. It didn’t just cancel its deal with RPO, but the entire notebook project. The reason, according to Thompson: It did some late market research and determined that because of the emergence of tablet computers there would be no demand for a notebook with a touch-screen.

Since RPO’s business plan was built around the revenue from that customer, the cancellation represented a material change and triggered a covenant on a loan the company had taken out in September.

Its equity investors, which include venture firms and corporate investors that poured $55 million into the dv5 battery business, were either unwilling or unable to put more capital in the business. RPO and its subsidiary in Australia, where the technology was originally developed, were forced into bankruptcy.

RPO’s touch-screen technology uses optical waves to detect touch, which is sensitive enough to recognize touch from a finger, a fingernail, a gloved hand, even a pen or brush. It also does away with the metalized layers in front of the display that impair the clarity of the screen.

So, what if you could use the brains and connectivity of such a hand-held computer to drive a laptop-size screen, keyboard and speakers, thus overcoming these limitations? Well, Motorola Mobility has devised a new phone and accessory that aim to do just that: to make the phone the only computer you need.

I’ve been testing this new phone, the Atrix 4G, an Android device that will cost $200 with a two-year contract and will run on AT&T’s network. It’s slated to be available by March 6. I’ve also been testing its unusual and clever accessory called the laptop dock, which looks like a large netbook, with an 11.6-inch screen, full keyboard, touch pad, and stereo speakers. This dock, the hp nc6400 battery price of which depends on when you buy it, has no processor, no file storage and no connectivity of its own. It’s dormant until you plug the Atrix into a slot behind the screen.

When you dock the phone, the faux laptop comes alive. It duplicates the phone’s screen on its larger display and lets you use its connectivity and apps. It also contains a battery that charges the phone. The image of the phone’s screen, and any of its apps you run, can be actual size or blown up to use the dock’s larger screen.

Even more interestingly, the dock gives you access to a full, and full-screen, PC version of the Firefox Web browser. Firefox is tucked away inside the Atrix but is available only when the phone is plugged into the laptop dock or a second, smaller dock that’s meant to connect to a TV or desktop monitor. The smaller dock lacks a built-in keyboard, hp pavilion zt1230  battery or screen.

The laptop dock costs $500, but AT&T will knock the price down to $300, after rebates, if you buy it at the same time you buy the phone. That brings the combined price of both devices to $500—the same as the separate price for the dock. The smaller dock, called the multimedia dock, costs $190.

In my hp dv4 battery tests, the Atrix and the laptop dock performed mostly as advertised. The phone had no trouble driving the larger screen or the full Firefox browser.