PortaPow Specialised 21AWG 5ft Charge Only Apple 30-pin Cable for iPhone/iPad Air/Mini iPod Touch
Normal charge+sync USB cables limit the charging speed when connected to a computer, TV or other data enabled socket. This allows you to get upto 2A, so iPhones and iPads can charge at a similar speed to your mains charged (depending on how powerful the USB socket is). You will not get the 'not charging' message when charging your iPad from a modern PC. iPods can be charged from sockets which won't charge with a normal socket.
This is also a robust cable which is supplied with a 1 year guarantee from PortaPow UK and uses thick 21AWG copper, for a similar charging speed to the original cable despite being 50% longer