feivel – I’ve seen people talking on it (or just the cell phone without the bluetooth) WHILE davening (one person took the call from the amud, and said “I can’t talk now I am in the middle of davening” — let the call go to v-mail or use the missed call feature and call back when you are available.
(OK a disclaimer: this excludes emergency response people, and perhaps men who have an expecting wife at home and the due date is NOW and other such scenerios)