transmission would be imposed on the cell phone's carrier frequency, but I would imagine the tower that is receiving the signal is only going to transmit a specific band of frequencies within the signal. Unless the signal of the fob falls to the range of the frequency of the vocal cord, it will likely be filtered out at the receiving tower. The way to tell if this would work would be simply to make a connection to someone with your cell phone, be perfectly quiet, and press the button. If you hear interference on your cell phone, it is duplexing back and it just may well work.