Thanks for the interest. Do you mean moving the hyphen such that the title becomes "Bioelectric Signal Analog-Frontend Module.."? I never did get around to learning how to use hyphens correctly.

In regards to addressing your question: If you are talking about having electrodes attached to the skin of the skull then it shouldn't be hard at all. You would have to have a higher gain since the magnitude of the signal on the skin is on the order of microvolts. As such, noise filtering is even more important but the areas to filter (line noise and high-frequency) remains the same as ECGs. If you are trying to pick up brain signals without touching the head such as in a capacitve electrode application then it is a lot harder due to field strength and, again, external noise.

As far as interpreting brain signals, if you were to segregate brain signal frequencies by bands* then it would be relatively straight-forward as you would just apply bandpass filters and look for how much spectral power is in each one. When one is higher than all the others by an empirically derived margin then you can assign that to a certain action such as activating a servo motor.

* People that were working with electroencephalograms (EEGs) have found that brain waves seem to have a certain frequency range associated with them depending on what the subject is doing. They have segregated this frequency range into bands and given them names such as alpha, beta, delta, theta, and so on. Example would be alpha which has a frequency range of about 8-12Hz and comes on when the eyes are closed. Beta waves become present when the subject is focus, alert,or thinking and can span from about 12-30Hz depending on how "focused" the subject is. Capture strength is also of concern in this regard as certain bands are more prominent than others in different locations in the brain such as the back of the head (occipital lobe) which alpha waves are most readily seen when a subject closes his/her eyes.

Now, if you are interested in trying to see if you can associate a certain frequency or waveform feature with a specific thought than that is a lot harder - many more orders of magnitude. As far as I am aware, there has been only research and it is not practical at this point in time.

I see what you did with your model number ;) care to move the hyphen one place to the left?

More seriously... how hard would it be (forgive blatant ignorance here) to engineer a device similar to this that could pick up brain signals from outside the skull, and have them come out reasonably intelligible...? Something, say, enough so that the brain in question could be trained to move a homebrew prosthetic appendage, but that also avoids involving surgery? (Figure that the appendage, electronically speaking, is two servo motors and a simple controller such as an Arduino or Teensy.)

Explain-like-I'm-five language when discussing bio stuff, please, even with the basics. I speak technology pretty well (I'm an electronics hobbyist with interests mostly in retrocomputing), but I know very little indeed in the way of biology or medicine...