Don't forget the battery, wifi and other electronics needed for fully functional system. It would make the entire device 5 times bigger. But its getting there when the entire system is as small as this.
I don't think you'd put a full system in a cable, but you'd make smart cables like Apple's lightning cable or their video adapters that actually convert signals.
Thin film batteries + solar cells are already being mass manufactured so thats not a problem. RF chips are shrinking rapidly too and you'd need little more than a CC3000 from TI which is already pretty small (16.3 x 13.5 x 2mm)
