С началом войны на некоторое время отошла от кино и посвятила себя практическм целиком научно-техническим разработкам в области вооружения:
to prevent remote-controlled torpedoes from being hijacked, she helped develop an early version of spread spectrum communication, which is part of the basis for wireless technologies such as Bluetooth and Wi-Fi:
Тот военного времени патент был реактивирован позднее: resurfaced in the 1950s while private companies were developing a wireless technology called CDMA. Lamarr's method is still in use today by cell networks, Bluetooth devices and Wi-Fi.
Almost three years before Lamarr died in 2000, the Electronic Frontier Foundation gave her an award for her contribution to wireless communications.