The whole of Back To The Future is essentially about time, so it's only appropriate that a suitably brilliant wristwatch should be made for it.
This brilliant Flux Capacitor watch is now available to buy on ThinkGeek. It tells the time and date using the lights in the middle. When you press the bottom button, three sets of lights illuminate, corresponding to hours, minutes first digit and minutes second digit - for example, 10 lights, followed by 5, followed by 3 means that the time is 10:53.
Meanwhile, the lower display shows the current date, but pressing the middle button activates 'Time Travel' mode, and the watch will display a random date - a la Marty and Doc. Whether you actually then travel to that time is not specified, but it'd be extremely good value if $49.99 (£32) gave you the ability to time travel. Mind you, you get some good value these days, so you just never know.
The band and case are made of stainless steel - just like DeLorean - it's officially licensed, comes in a presentation box and you can head here to get yours. About time too.