Harmonic drives (also called strain wave gear) was invented in 1957 by C.W. Musser. They offer several advantages over conventional gear systems, especially for high precision and high torque applications. Hence, they are commonly used in many industrial robots. High gear reduction ratios are possible in a small volume from 30:1 up to 100:1 in some cases!
The patents regarding this technology were held by Harmonic Drive AG. (Now expired, but the company holds the Trademark for the term Harmonic gear – a generic term is strain wave gear). It would be great to use these motors for my application, but typically, these drives are very expensive, costing upwards of $1000 per set! I guess I will need to look for cheaper solutions or make one on my own?
An excellent video describing harmonic drives from Harmonic Drive AG: