Not as convenient as an all-in-one boxette widget but...
External 1TB USB drive from Ebay - £55
Raspberry Pi - £30
Wifi Dongle - £3.50
Might need a powered USB hub depending on the drive, but then you can just keep adding them at around £55 a pop and almost get 3TB for the same price ;o)
Of course the all-in-one is handy if you're carrying data around to different places but not everyone is, though you'd just take the USB drive with you in that case and leave the pi at home.
Just sayin' ;o)