At first glance, the OneCable seems like just an over-sized USB to iPhone cable. But look closer and the extended head hides two other connectors, neatly daisy-chained to plug into each other. So the miniUSB one plugs into the back of the microUSB one, and so on.
All the pins seem connected for data too, and I had no problems syncing the Lumia 800 shown (below) to my desktop. One possible omission is that there's no Nokia 2mm connector, but then I can't think of any recent Symbian smartphones that don't also charge using microUSB if needed, and several, plus the Windows Phone-powered Lumia range, all charge by microUSB alone.
miniUSB is far less common in mobile these days, but there are still plenty of cameras and other gadgets which use it, plus there's a good chance that you or one of your family has an iPod, iPhone or iPad - in my experience these can be a bit fussy about charging and syncing, but my family iPhone and iPad both seemed to charge and sync happily enough, so thumbs up on this front too.
At its simplest then, you could have just this gadget, a mains to USB adapter and/or a 12V USB adapter and you'd be set for charging most devices you come across. Which is pretty cool. In its data cable section, Mobile Fun's OneCable is just under £10, which seems about right considering the three-way connector link-ups it contains.