If anyone is interested, we have been working on a new kind of Servo, that is USB controlled and uses 2.43mA (vs 100mA for MX-28 / 64) when not moving and has the possibility to drop down to 100nA when in standby to preserve the battery.
A later version may well use USB 3.1 which allows 12v at 5A down the USB cable so only one cable would then be required. But we have to wait for the standards board co confirm the new specification in July.
It is likely to be exactly 153% of the size of a MX-28 servo and initial indications are it will be between 40 & 50 Kg/cm of torque. (i.e. print poppy at 153% scale and just add these new servos, so poppy would now be 128.5 cm tall).
This means that if you print out a version of poppy with only MX28 servos at 153%, you are all ready to go (though the internals of the head will also expand)
Further, this servo has a JTAG debug port and open source RTOS on it so people can expand it and add their own routines, as well as it has a 3D accelerometer, current sensor, temperature sensor, can detect if the motor power is lost and in ASCII mode can be controlled simply via any program (even a terminal emulator) and looks like a standard serial port over USB (i.e. a CDC device) and has been tested on OSX, Linux and Windows.
We are looking at a binary mode where a user can use LIBUSB and Python (as an example) to control the servos and react to various thresholds, for example if the servos detect a freefall or sudden knock, it can interrupt the host and interact in whatever manner is required.
We have built the initial prototypes, and are looking at build the new scaled up prototype that I have mentioned above.
The price is going to be much cheaper than a MX-64 or 28 and runs at 11.1v (i.e. 3S LiPO battery)