Yes, it definitely works! Researchers concluded that the EMS did indeed cause significant effects on decreasing waist circumference, abdominal obesity, subcutaneous fat mass, and body fat percentage.
Studies confirming some benefits do exist. A team led by Professor John Pocari, exercise physiologist at the University of Wisconsin, recruited 72 women who, at the time, did no lower-body training and assigned them to one of three groups. For six weeks, one did nothing different, one was assigned a regimen of lower-body strengthening moves and the third used an EMS buttock toner. At the end of the trial, both activity groups reported improvements in the shape and tone of their posteriors. And tests revealed that gluteal strength increased by 9% among the exercisers and 15% among those subjected to electricity. Muscular endurance (the ability to contract muscles over time) also rose: by 26% among the regular exercisers and 29% among those who had used an EMS device.