Machine Exercises
The use of machine to aid in abdominal strength is not essential, especially with the full range of alternative exercises that can be found using the above links.
The health and fitness industry has many gimmicks, and as such millions are wasted by people thinking that the latest products their buying will aid them in achieving the 6-pack they have only dreamt about.
The key is not the machine, its how you use it, how often and controlling your diet and exercise, avoid wasting your money on every new product that comes out.