However much smartphone manufacturers emphasize the usability of their latest devices, one fact is undeniable: smartphone keyboards don't hold a candle to their desktop cousins. While this may not matter for SMS, a few calendar entries, or even the odd quick email, smartphone keyboards become tiresome for any significant amount of typing.

The latest S60 devices are shipped with a built in external keyboard driver. This allows standard Bluetooth technology keyboards, including Nokia's own foldaway keyboard, to be used with an S60 device. However, a number of portable keyboard manufacturers take a slightly non-standard approach to keyboard design. For example, the built in S60 keyboard driver maps the left and right Windows menu keys to the left and right softkeys on an S60 device, but iGo's Stowaway keyboards have dispensed with this right Windows menu key. This means that, using the default driver, Stowaway keyboards cannot provide full interaction on an S60 device.

iGo has now release a driver for S60 3rd Edition devices. Don't let iGo's somewhat incomplete driver download page put you off, the driver appears to work with all S60 3rd Edition devices, although I've only been able to use it in anger on a Nokia N80 and Nokia N93 (one of the devices currently not listed on the download page) and briefly on an Nokia N95.

The new driver differs little from the one available when I reviewed the Stowaway Universal Bluetooth keyboard back in 2006. The latest driver offers the same features for pairing, setting key repeats and delays, selecting a secure connection, and mapping applications to specific keys.

Closed the Sierra is about the size of a passport and as thick as an average monoblock S60. The case is protected by a stainless steel shell. This contributes to the Sierra's weight, which is almost twice that of the Universal. The steel shell does not completely protect the close keyboard, as part of the hinge mechanism and keyboard housing are exposed around the edge. Despite this, the Sierra feels solid and gives the impression it should cope with everyday knocks and drops.

The Sierra is opened with a latch on the long edge, opposite the hinge. The keyboard then concertinas open through a W configuration before lying flat.

Once the keyboard is fully open, the two outer sides of the keyboard are slid in and the Sierra is ready for use.

Once open the Sierra needs to be paired with your S60 device. In one way this task is more straightforward with the Sierra than the Universal, thanks to its additional fifth row of numeric keys. These leave you in no doubt as to the keys to press to enter the pairing passcode. There is one small issue with pairing the Sierra however, one which will be unique to S60 owners. To turn the Sierra on and into "discoverable" mode you have to press a small button located above the dash (F11) key. To press this button you really need something not unlike a PDA stylus, something S60 device's lack.

Fortunately, the "discoverable" button needs to be pressed rarely; when you want to use the keyboard with a different device. When this need arises a biro or bent paperclip comes in handy.

Once ready the Sierra presents a fairly conventional keyboard, with the same key size and spacing as a standard desktop keyboard on five rows. In addition to the standard keyboard functions the Sierra also offers a number of smartphone specific features. The most prominent is a set of shortcut keys on the right hand side of the keyboard. These provide access to the calendar, contacts, messaging, and web applications. These keys cannot be reassigned. While this is not a big issue, it does mean that on an S60 3rd Edition device the Web key opens the XHTML browser, not the Web Browser for S60. However, the Web Browser for S60 can be mapped easily to open from one of the keyboard's function keys.

In addition to these dedicated keys a number of the standard keys also have additional smartphone functions. These are marked in blue on the key faces, however not all the marked functions have an effect on an S60 device. These additional functions are activated by pressing the function key (which sits to the left of the space bar) in combination with the smart key.

The most crucial of these smart keys are the left and right space bar keys, which map to S60's left and right softkeys, thereby providing access to the Options and Back menus. Fn+J provides the same functionality as the S60 menu key, including a long press activating the active applications list. Confusingly the J key is marked "Today," while next to it, the K key is marked "Programs." So, the K key would seem the logical one to provide the S60 menu key function. However, as the smart function labels are not overpowering this incongruity is soon forgotten.

In addition, the D and F keys gain extra functions when in the standby or phone screen. If no number has been entered, Fn+D opens Contacts. When a number has been entered Fn+D starts a call. Fn+ F ends an active call. The manual states that the numeric keys can be used to dial a number in the standby screen, however this did not seem to work on a Nokia N93 or Nokia N80. However, I don't see this as a significant drawback given how rarely any user is likely to be manually dialing numbers while using the Sierra.

The M key provides a shortcut to the S60 device's settings options. Euro, Yen, and pound (sterling) symbols are available directly from the keyboard. Further symbols and international characters are available from combined key presses.

As mentioned earlier, the driver allows the Sierra's F1 to F10 keys to be linked to applications on the S60 device. This is simple to set up and very handy for accessing your favorite applications, without having to navigate through the S60 desktop.

The Sierra also includes a phone stand, which is stored underneath the keyboard. While it is very handy for monoblock or tablet S60 devices, I do worry that it might be easily mislaid.

Overall the Sierra is designed well. The layout is close enough to a desktop keyboard to make any transition between the two straightforward and natural; because of the Sierra's full five row configuration that provides direct access to numbers. The key layout is good, however - depending on how expert a typist you are - there is one possible flaw. The delete key is immediately to the left of the left cursor key; making it possible to delete a character rather than moving left and vice-versa. I didn't find it a big issue, but it did cause the occasional frustration.

If the Sierra has a real limitation it comes from the design of its folding mechanism. While the outer hinges are locked. by sliding the outer keyboard sections in towards the center, the central hinge remains unlocked. This means that any attempts to use the Sierra in more spontaneous settings can be challenging, as it constantly bends in the middle. This means the Sierra is best suited to use on a flat surface.

The Sierra is certainly a good keyboard. The key action is positive and the key travel feels very much like that of a full sized desktop keyboard. The dedicated keys for common smartphone functions are useful and the overall interaction with S60 is very good. In fact, the Sierra and Universal highlight how much of a limitation the standard phone keypad is to the S60 interface. While S60 does an excellent job of achieving usability from a phone keypad, it is amazing how much more efficient it is with two hands and a few extra keys. The design of the Sierra is however best suited to working from a desk or similar flat surface. For this reason, and the fact that the phone stand is not integrated, I personally would prefer to pack the Universal; it offers greater flexibility to work on the go and in inconvenient locations that lack flat working spaces. But, if you feel the need for a keyboard for your S60 device mainly when in an office, the Sierra is the Stowaway to choose. Either way a Stowaway should be on any S60 road warrior's must have list of accessories.

Note for UIQ 3. There is currently no driver for UIQ 3 for either Stowaway keyboard. A driver is under development, but no release date has been announced. Without the driver the Stowaway keyboards can be used with UIQ 3 phones for typing, but offer no practical way to control a UIQ 3 phone's functionality. However, given that UIQ 3 is designed to work with keypad only phones, the UIQ 3 driver should offer much tighter integration with UIQ 3 than the UIQ 2 driver achieved. When the UIQ 3 drivers become available, I'll report on how they work too.

More information on the range of Stowaway keyboards can be found at www.igo.com.