Honestly - this is probably my favourite gadget related purchase of the last several years, simply because it has had such a useful impact on EVERY gadget I have!
The concept is simple: Got a cable? Could it be tidier? Cut some of this to length, wind up cable (Loop it or fold it into a useful length) and then wrap the strip around it.
I have reclaimed so much space from various kit boxes by just tidying up the cables properly - it also makes you look more professional when you turn up somewhere with a kit box and everything is sensibly packed!
I may need another 5 metres....
I suppose it could be useful in a recreational setting too..... :-D