The WISE/SDSS selected hyper-luminous (WISSH) quasars survey is an extensive multiband observing program (from millimeter wavelengths to hard X rays) to investigate the role of nuclear activity in SMBH-galaxy self-regulated growth via extended outflows. Our ongoing project is designed to accurately constrain both AGN and host galaxy ISM properties in a large sample of ~ 90 broad-line quasars at the brightest end of the AGN luminosity function (L_bol > 1e14 L_sun) and at the peak of their number density (z ~ 2 - 4)I will review the most relevant results obtained to date with emphasis on the discovery of extremely powerful (up to ~ 4% of L_bol) ionized outflows, the relation between AGN properties (obscuration, luminosity and Eddington ratio) and large-scale winds, and the SED of these hyper-luminous quasars.