Is it right, that blood pressure is mainly measured with the "oscillometric technique"? What does that mean?

No, at the physician practice they use the well known "sound method", where heartbeats are listened to by a stethoscope.

The "oscillometric technique" uses another measurement process. Most of the now available devices for measurement use this method. Electronic microprocessors in oscillometric devices calculate blood pressure data from pressure fluctuation (oscillations), which arise from the occuring pulse. Because of the irrelevance of heartbeats for this method, neither a microphone nor a stethoscope is necessary. The measurement value are displayed optically. But with an irregular pulse, a visit at the doctor's is recommended.