Hi,
Millimeter wave technology has been a good area of research these days. applications range from defence to commercial. 77GHz band is intended for collision avoidance systems in Vehicles. In defense for Radar applications, cosmology's been there for space exploration for quite some time. As we look for compact wireless systems, its quite obvious we shift for these millimeter wave technology. In short think of any short range wireless application is eligible for millimeter wave technology.
Substrate integrated waveguide antennas, Planar slot antennas, aperture type are few of antennas i could think of now.!!