He introduced complementary sequences. Those are pairs of binary sequences whose autocorrelation functions add up to zero for all non-zero time shifts. Today they are used in various WiFi and 3G standards.
^D. Klocke, A. Schmitz, H. Soltner, H. Bousack and H. Schmitz, "Infrared receptors in pyrophilous ('fire loving') insects as model for new un-cooled infrared sensors," Beilstein Journal of Nanotechnology2, 186 (2011), doi:10.3762/bjnano.2.22
MARCEL J.E. GOLAY (1902-1989) obituary in the June 1990 IEEE Information Society Newsletter (by James L. Massey).