[martinchaen]

Meaning that trodes use ultrasound to interpret the signals your brain is sending, not that you can use trodes as an ultrasound sensor. I wouldn't even allow someone with a passive ultrasound sensor pick up a character wearing active trodes, because the broadcast range of trodes should be 0. They literally have to place their head on the sensor for  it to detect the trodenet, in my opinion...

[Mithlas]

Those types of sensors may also rely on things like bone conductivity and the properties of living tissue in order to get the information they need. I think that supremely sensitive electromagnetic sensors are the best brain scanning we can get without being able to go into the brain to measure sugars and neurochemicals directly, but it's been a while since I dealt with applied biopsych.