Lawrence Jones explains the function of Nancy Guthrie's pacemaker and how its data is crucial to the investigation. The pacemaker continuously monitors heart rhythms and sends data via Bluetooth to a smartphone or bedside monitor. It stopped syncing around 2 AM on February 1st, indicating a loss of connection from her phone and Apple Watch, which were left at home. This loss of connection helps investigators establish a vital timeline for her disappearance. The segment also touches on the use of a 'signal sniffer' from helicopters to detect the pacemaker's signal.