charge ipad4 while equipment is connected

So I seem to be a poweruser of Apple's iPad, meaning that I MUST find a way to charge my iPad4 (and also my iPhone5) while equipment is connected to the lightning port. Is there some sort of lightning hub or anything that lets me connect a device AND charge the iPad at the same time?

I use an Audio-Interface or Line 6 Mobile In and when I play guitar the battery drains pretty quickly.

Thanks for any suggestion.