Some third-party Lightning accessories show warning messages in iOS 7. Rest assured if you buy a Lightning accessory from Mobile Fun, it will work with your Apple device for both syncing and charging – just dismiss the warning and continue using your accessory as normal.
The reason this message is appears is that you are using an accessory that isn’t Apple certified. Accessory manufacturers choose to forgo the costly Apple certification process to keep retail prices down, while still providing products of equal quality.
Each time Apple update their software, there’s a risk that additional third-party accessories may begin to display warnings and functionality may be affected.