AKG MaxModular, 60 Watts, 27.5 lbs, with handle.
Can be powered by internal rechargeable battery (or AC).
Optional wireless receiver.
So no audio cable and no power cable.

But $$$. $1200 per speaker, plus hundreds more for transmitters and receivers. And not specifically designed for keyboards. But the right idea, I think.

Clif,

Nice idea but I would never relie on batteries and spend lots of money, just to 'save' a powerchord. Realize your transmitters need a signalcable and power connection and need space in your audio-rack too.
I could live with purchasing a wireless microphone for 'mobile' use but never saw a singer/musician moving his speakers while performing .

Roel