The BBC has an article about a new type of goggles designed by an industrial design student named Katie Williams. They are called the “Inview Goggles” and they feature a small compass which tracks when you change direction in the pool. They can tell you how many laps you have swum and how long you have been swimming.
This strikes me as a good idea. Granted, they will need to make the electronics smaller than the current size (the size of a small stone) but I might consider looking into these once they get on the market, if they are not too expensive. It would be very useful in training to be able to concentrate more on stroke and form and less on how long I’ve been swimming.

[...] Even easier than using a wristwatch, you could get a set of goggles that automatically counts your laps for you through the use of a small compass and displays the lap count and duration of your swim on the lens [...]
[...] taking a cue from Katie Williams’ “Inview Goggles,” German company Rodenstock has developed a prototype set of sunglasses that can display your [...]