Low-cost open-source active electrode to measure EEG

Tiny but very accurate active electrode, we are still in the process of setting it up, analog circuitry takes time, but we would like to know your opinion, how interesting are such devices?
This is a very small format, including a low noise power supply, two-stage amplifier, controlled right leg, bandpass filter (4 orders), 16-bit ADC to measure EEG, EMG, EKG, etc that you can integrate into your device. The diameter is only 20 mm.

So if you would like to buy an EEG device, open-source and low-cost active EEG electrode let us know.