It is here. The mystery invention was unveiled on December 3.

after months of speculation following an enigmatic reference by its inventor Dean Kamen last January.

Mr Kamen, a prolific inventor of devices as diverse as a portable dialysis machine and a motorised stair-climbing wheelchair, described IT as an alternative to machines "that are dirty, expensive, sometimes dangerous and often frustrating". Expectations were heightened by the high profile of some investors in the project, including Amazon chief executive Jeff Bezos and Apple's Steve Jobs, who was quoted as saying architects should base designs for entire cities around IT.

So, what is IT? Segway, as IT has been re-named, is a motorised scooter, the "world's first dynamic self-balancing human transporter".

It looks like an old-fashioned manual lawn mower but has gyroscopes and tilt sensors which monitor a rider's centre of gravity 100 times a second to keep him or her upright. If he or she leans slightly forward, the Segway moves forward. When leaning back, the Segway moves back.

The machine has a top speed of 12 mph and each battery has enough juice for a 15 mile trip.

Even before its launch, the Segway had the US Postal Service, General Electric and the US National Parks reportedly agreeing to buy a number of the heavy duty models for £5,600 (8,000 dollars) each.

The £2,100 (3,000 dollars) consumer version will not be available until next year.

If you are looking for an alternative antidote to traffic gridlock, you should get hold of the amazingly-addictive Rush Hour, a puzzle game which has you shifting plastic cars and trucks around a square of plastic road until you have cleared a way to the exit. There are 40 challenge cards and four levels - beginner, intermediate, advanced and expert. The most difficult takes a bit of cracking, which is why the game (now back in vogue) has won so many prizes, including an American Mensa award.

You can buy it from Firebox, the toys-for-boys web site, at a fraction of the cost of a PlayStation 2 game or road test various unofficial online versions first.

If you do decide to take the Rush Hour plunge, prepare to lose interest in your video games console, friends, family and work-related Christmas parties. Once you get the real thing in all its plastic glory, wave goodbye to Freecell and Minesweeper, put your mouse away and drive.

www.segway.com/consumer/segway/
www.firebox.com
igoweb.org/wms/rushHour/
www.eagle-i.com/JAVA/rush.html