The battery life isn't so great...

No need to be excused for any noob-iness if you have a genuine question

As you can imagine, the N900 runs the programming to activate the servos (motorised joints for each limb). If you click on the link you will see that that the robot also has a printed circuit board (PCB) that the servos connect to as a an interface to distribute each command sent from the n900. Hence the need for the cable attached.

The circuit board also has has an external power supply attached using LiPo battery to feed the juice to the servos.

Hope this helps?

If we're to be specific... From thread:

Following software runs now on the N900:
- ROS
- OpenCV
- gstreamer (640x480 H.264)
- fcam (used intitially for autofocus etc)
- VNC / SSH (for remote access)

I wrote an ROS node for the N900 accelerometer and played a little bit with OpenCV. The face detection speed on the N900 was a bit disappointing though (0.25 fps) and I decided to stream the video to my PC (using gstreamer for which exists an ROS integration). Streaming causes only about 20% CPU utilization (640x480 resolution / H.264 / 1500 KB/s) on the N900.
Less complex tasks like color based tracking should be able to run on the robot itself with acceptable speed.

Computational tasks (distance analysis from cam feedback) most likely were run from a desktop PC, even at 1150mhz N900 alone most likely couldn't handle it.

Just noticed: That or what MINKIN2 pointed out, possibly both

Looks absolutely great. Love the updated N900 mount that looks like a horse head too.

I'm currently looking for a stepper motor controller, are there any particular cheap ones you can recommend or do you build your own?

For stepper motors of that size, RS and Farnell can supply them. However the these robots often use the same servos the you will find in any hobby grade RC cars and come in a variety of sizes, torque ranges and turn speeds.(those pictured above appear to be futaba by manufacture)

I too would love to build one of these. I was trained as a mechanical engineer, my other hobby is RC cars and have a good understanding of the power systems and motors used for this,and have previously built a cybot just for fun...
http://lpilsley.co.uk/cybot/graphics/robo-mag.gif

My problem has always been that whilst I have the mechanical understanding to build the machine, I still don't fully grasp the software to operate these things. I still have my cybot and would love to have the n900 control it. Shame they never released the software for it.

This and vid of N900 controlling quadcopter (http://www.youtube.com/watch?v=kS3_aGWFBRs) make me hum Terminator theme in my nightmares, Skynet can be built on maemo

Dude, this is awesome!!!!

I don't know why I am amazed at anything this computer can do after all I've read about & done with it myself, but somehow there's always more.
Thanks for sharing, I'm thinking it'll be the next world super power with nukes next. Game over iPhone, GAME OVER

Not sure why but that sentence had me thinking of the cold war and "da Mann" with his finger on the button!

The reality though is not quite the same as he would be trying to laugh maniacally whilst crow fingering Ctrl+Shift +Q keys

The N900 is working as the core cpu (brains) of the robot, and it actually uses camera to "see".