Tummy trimming machines are never successful.
Your midriff paunch will not be melted by just performing any amount of abdominal exercises. This fat needs to be brought in the metabolism with proper aerobic exercises.
The fat from the waist is mobilised and converted into fuel during aerobic exercises. For burning just 1 kg of waist fat, the abdominal muscles will have to create an output of 7000 calories and for that you will have to perform about 10,000 sit-ups. This can result in severe overuse injuries and still not giving any results.
The best way I would suggest is to do abdominal exercises and get a very good tone for your abdominal muscles and a good posture rather than aiming to burn your midriff fat. Combine it with any aerobic exercises (walking, swimming, cycling) and a proper diet and you should have a flat midriff.