Is it Feasible to Make an E-Field Proximity Sensor With Arduino?

Inspired by the theremin and a general interest in proximity sensing, I was wondering if it would be possible to employ the use of an electromagnetic field and a microcontroller to detect when the field is disrupted by some conducting material (Like a person's skin). I've built an EMF detector with Arduino before, so I'm thinking I can use the same methods to detect the field I will create. However, I'm not entirely sure yet how to create and sustain the field (Perhaps inductors?), and I'm not sure how large/strong I need to make the field in order for some conductive material moving through it to make a significant enough change in the field to be detected by the Arduino. Any help is appreciated, thanks.

Basically, you are talking about capacitive sensing.

Paul__B: Basically, you are talking about capacitive sensing.

Awesome, thanks.