Not sure what the ab coaster is but needles to say if you seen it on TV it is most likely no good, Watch what you eat, Eat lean whole foods, What results did you want to achieve? If you want to lose weight just do cardio, Cross trainers are the best but it depends on you prefrance, If you want to get abs do crunches with weights also Them big balls do a great job also, Hope this helps
there are much better ab/core specific exercises if you wanted defined abs (make them look like stacked bricks) and THEY WORK.....but diet is really important
I agree diet is super important......I like the P90X ab ripper exercises along with other core related routines