Technofile: When it comes to finding the smartest smartphone out there to complement your digital lifestyle, the field can look pretty wide.

But there are plenty of smartphones which are actually pretty dumb.

Consider the requirements for the ultimate business phones. It needs to be able to perform the basic functions of a phone without any fuss. It needs to give instant access to text and e-mail messaging with the best software. And because of that - sorry, no arguments - it really does need a keyboard.

Forget trying to create a complex reply to a business colleague using T9 predictive texting.

You'll soon give up when the automatic dictionary keeps correcting your technical language with words like Paris and kitchen. No, a keyboard is essential.

Next up we need an operating system running on the phone that isn't so dumb that you can't run third party software on it.

That discounts phones that are effectively hard-wired to perform in a certain way. If the phone can't be adapted and changed, then bin it.

In essence that means the field is narrowed down to four handset makers: Nokia, Sony Ericsson, PalmOne and any handset which runs Microsoft's Pocket PC operating system.

Firstly, Nokia. The 9300, 9500 and 6822 models are the only ones with keyboards. Let's junk the 6822 as it's not very flexible on running software, although the packaged suite is workable enough. The fold-out keyboard, though innovative enough, is fiddly to type on. The former two are much more in the industrial strength category, but they are bulky and more inflexible in software terms.

But with Nokia at least you know you are getting the best user interface money can buy.

A little like the legend that no one ever got sacked buying IBM, you can't go that wrong with a Nokia.

Next up, Sony Ericsson. Here the main contender is the P910i. This is getting closer to the ideal.

The Symbian operating system is flexible, the software extremely good, the form factor is great, plus it has all the fun stuff like a camera and MP3 player.

Its keyboard is very handy, but it does feel flimsy compared to some. This is a real contender of a smartphone.

For our Microsoft Pocket PC phones let's look at the most innovative on the market. 02 sells the XDAIIi, but canny buyers will notice that a version with a keyboard can be got online under the own-brand of Qtek or i-mate. These clever quad-band GSM/GPRS phones feature integrated Bluetooth and WiFi connectivity as well as all the Microsoft Office tools you'll need to work on the move. Plus the slide-out Qwerty keypad makes it almost a replacement for a laptop while travelling. Definitely a phone worth considering.

It's worth noting that Hewlett Packard plan a new iPAQ hw6515 Mobile Messenger which is also worth a look when it's out.

Lastly, there's the relatively recent version of the Treo PDA phone, the 650 model. Here we have a lot of phone in one package.

A great operating system which can run a ton of third party application which will make your life easier.

It has a camera, great messaging capabilities and Bluetooth.

No Wi-Fi, but this is less useful than the quad-band capability.

Perhaps most useful of all is that it has the best keyboard of any smartphone on the market - something you'll appreciate when hammering out that crucial message on the way back to the office.

Its use of SD cards means you can pack as much as a gigabyte of memory into it. More than enough for most. And the phone will easily synchronise with a myriad of office applications. You can literally carry the office around with you.

In the realm of the smartphone I'm still waiting for the perfect combination of form and functionality. For now the P910i, Treo 650 and the Qtek are the best I can find.

Rumour has it that Nokia will next week come out with a range of new phones so let's hope they produce the goods.