By varying the thickness of the layers in a multilayer down through the structure, it is possible to produce wide-band reflectors. We report measurements and modeling of the reflectivity of Ni/C, Mo/Si and W/Si supermirrors, at energies ranging from 8 to 130 keV, and discuss the performance of two possible applications: a Kirkpatrick-Baez telescope, and a multiwavelength hard X-ray focusing reflector. The supermirrors perform as expected, and model-fits over the full range have been attempted with some success. We conclude that the supermirror coatings do indeed look very promising as hard x-ray optics for synchrotron applications, while some work on highly nested structures and supermirror coatings on very thin large substrates is necessary, before the feasibility of employing large-area supermirrors for hard X-ray astronomy is determined.