(See samples of the voice skins, right). One site even offers Warnie and Kylie voice skins - although they sound more like Kiwis than Australians.

But now genuine celebrity voices are joining the clamour with GPS device maker TomTom offering royalties to personalities such as John Cleese for each customer download of his own brand of voice commands. The company, which already markets around 55 novelty voices for customers to download, has just announced plans to evolve the market even further with a new content-sharing platform. This will allow its users to create their own voice skins, warning sounds, and start up images to share with other community members. ----------------------

Do you use novelty/celebrity voices on your GPS? Let us know at scoop@smh.com.au.

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A star rating system will also help members to find useful community content, and enable automatic updates to their selected content, such as another's list of favourite restaurants. "Our users tell us all the time how much they enjoy personalising their devices with content they can get from one another. However, this content has always been spread out and unorganised across the web and on users' devices," says Chris Kearney, TomTom's local marketing manager.

TomTom is the first major supplier to truly embrace this level of personalisation and Mr Kearney says its system architecture allows third-party developers to build voice add-ons much as they did for mobile ringtones many years ago. "Because our devices are reasonably open, others can easily build content for it. While we do not endorse these add-ons, I think they do encourage interest in the category over all and help to make people aware of what voices can do," he says. None of its main competitors in Australia have announced any plans to follow TomTom, with many choosing to focus on other product developments.

GPS manufacturer Navman says internal company research indicates novelty add-ons are not a high priority for its customer base and Garmin says its development focus is on making "travelling as stress-free as possible". Mr Kearney says although the voice skin market does not represent a core source of revenue for TomTom's business, it does add a little bit of fun for users without compromising safety.

Despite the comic and sometimes irreverent nature of some of the voice skins, Mr Kearney claims they are unlikely to disrupt a driver's concentration. "Its no different to when you are talking in the car to people or listening to the radio - the device is really just giving instructions. It's the same as the mobile phone story. You don't text when you drive and don't touch the navigation screen when you drive." A study jointly commissioned in the Netherlands by TomTom, an insurance company and a car hire company found satellite navigation systems had a positive influence on road safety.

Of the navigation system users surveyed in the report, 62 per cent agreed with the statement that navigation systems made it easier for them to keep their attention on the road. An independent observation study was also conducted on driving ability and found there were "fewer occasions of unsuitable driving behaviour on the routes chosen when a navigation system was used". Anne Morphett, a senior adviser in road safety at NRMA Motoring and Services, says: "Although some of the voices available for people to use might seem a little tacky, the thing in their favour is that it is much safer for people to have instructions in an audible form than looking down at the device or a map. Anything that keeps focus - and particularly vision - on the road will enhance driving safety."