Gekkomat (for sale at 49,000 Euros) uses suction and compressed air cylinders. (So perhaps a venturi for vacuum? -- in which case efficiency would be low). Notice the foot attachment mechanism and the provision for the hands to ensure that the loading is mostly in the vertical plane, to reduce required pull-in forces. Something comparable will be required in our case.
(Gekkomat in Wired Magazine - Download attachment below for higher resolution version)