NEW YORK - You might think your smart phone is pretty brainy, but is it clever enough to essentially replace your laptop while on the go?

Salt Lake City-based Celio Corp. is betting you want a bit of both devices at the same time. It has come up with Redfly, which looks like a tiny laptop, but is actually a keyboard and screen that harnesses the processing power and storage space of smart phones that use Microsoft Corp.'s Windows Mobile operating system.

It does enhance some phone features, but given its price, relative chunkiness and limitations, I won't ditch my laptop -- even part time -- for one of these just yet.

I tested the more full-featured Redfly model, the C8N, which weighs 2 pounds and costs $299. A smaller model with slightly fewer bells and whistles, the C7, costs $199.

Like "netbooks" -- portable computers that often cost less than $400 and feature small screens and keyboards -- the C8N sports an 8-inch screen, a touch pad and a keyboard that is about three-fourths as large as a standard keyboard.

The C8N has USB ports, so you can plug in a phone and a thumb drive or mouse. There is a port for attaching a larger monitor, too. The device also has a non-removable battery that is rated for eight hours of use per charge.

I tried the C8N with two Samsung smart phones -- a BlackJack II and an SCH-i760, both of which run the Windows Mobile 6 operating system.

Setting up a phone with the C8N is pretty simple. After downloading and installing the appropriate driver for your phone, you can just plug it in with the USB cable or link it to the Redfly wirelessly, with Bluetooth. However, plugging it in directly will charge your phone, even if the Redfly is not connected to a wall outlet.

Once the Redfly recognizes your phone, it takes over. Whatever you would usually see on your phone's tiny screen shows up on the Redfly's comparably spacious one, and you can navigate with the C8N's touch pad or full keyboard.

If you've ever wished your smart phone's screen was larger, you'd be pleased to see it magnified on a Redfly. I found it easier to navigate basic functions this way, and I liked seeing my photos blown up.

The screen and keyboard made it easier to instant-message friends and type e-mails, and they enhanced Microsoft's Office Mobile software, too -- it was simpler to type and view Word documents. Business users could show a decent-sized PowerPoint presentation with the device.

Unfortunately, since the Redfly magnifies what you'd normally see on your smart phone, the Web will look pretty much the same. If your phone already redirects you to the more lightweight mobile sites when you try to visit Facebook or MySpace, that won't change -- they'll just be bigger. On the plus side, it's a lot easier to read news stories and look at photos on the Web with a larger screen, and type Web addresses with the keyboard.

But while the C8N's keyboard is much larger than the QWERTY keyboard on any smart phone, it's still quite tiny. I struggled with it at first. Eventually I felt less like an ogre clumsily pecking at elfin keys, but the keyboard still felt pretty cramped. And I ended up using the keyboard's directional keys for a lot of navigating, especially with the BlackJack II, since it didn't seem to recognize mouse clicks much of the time.

I also found it odd that both the battery and power indicators are over on the side of the Redfly, near the power button. I'd never look there to see my battery status unless I was turning the device on or off.

Another gripe: You can make and receive calls while your phone is connected to the Redfly, but there is no microphone, speaker or headphone jack on the device. So you either have to pick up the handset to talk or use a Bluetooth headset.

Similarly, if you want to listen to music stored on your phone or a thumb drive, you control it through Redfly but the sound will come through the phone.

I was hoping that videos would look cool on Redfly's screen, but wasn't really impressed. I tried watching some clips on the BlackJack II through a service called MobiTV, but they were choppier on the C8N than on the phone, even when I used a USB connection.

Perhaps I'd be a bigger fan of Redfly if it were skinnier, cheaper and worked on more operating systems. Celio said it is working to get Redfly hooked up with Apple Inc.'s iPhone and Research In Motion Ltd.'s BlackBerry, as well as phones that run on the Symbian software and Google Inc.'s Android software. And while the cheaper C7 is an option, I wouldn't want its smaller 7-inch screen.

Celio expects the Redfly's price to decline over time as the market for the product grows. For now, though, the device seems like an interesting idea that doesn't quite bridge the gap between smart phone and netbook, even if you've got a whiz of a handset.