I think that a 4-pole 1/8" jack would be the way to go; I realize not all devices use the same assignments, but that can be dealt with, and have one 1/8" jack. The power issue is a bit more complicated, but a USB port would do; much as I dislike the hijacking of a data standard (with power negotiation specified!) as a raw power jack, it's a fact of life. Then you don't have idiots like me who don't use iPods griping about it.