I love this idea , clever GWU !Another item you may want to look into is a Raudive diode. It is a mic coil but no diaphragm is attached to it so it only responds to spirit voices, nothing acoustic will be picked up by it. Digital Dowsing (Bill Chappell's company) sells one for under $40 that will work with any recorder with a 3.5mm audio input.
We like to put the diode on one channel of a recorder, and an acoustic mic on the other channel, to keep everything in context and sync'd.