In my opinion, the vast majority of products that you see on the television that are advertised to flatten your stomach are no where near as effective as what they claim to be (most of which I highly doubt are effective at all relative to a sound workout regime). There is very little (if any) scientific backing to many of these products. The main idea behind them is to generate profits by making outrageous claims that are simply too good to be true.
Consider how long these products actually last on the market. Years down the track they are taken off the shelves while something new and exciting replaces it. It's all marketing - the hype has died down because hardly anyone achieves any results. So in order to revive the hype, a new product is released. This is what is known as your fad product - they have been around for the last 30 years. Think about it, if these products really were that great then why on earth would they not render your basic (and proven) exercises obsolete?
The models on the commercials - of course they have been training for years upon years! I feel that it is heavily implied that they have only used this machine to attain a great figure...I can say with absolute certainty that this is not the case at all. If you ask them how they attained their physique, it would have most likely been through a more standardised program (ie. lifting weights combined with a sound diet and cardio routine). Not a fad product.
Sometimes the host actually goes outside and asks passers-by if they can "feel the muscle working". Whilst one may feel the abdominal muscles being used, this does not mean that it will assist the abdominal muscles to grow (or to burn a significant amount of fat either) - it simply means that they are being used...nothing more.
A flatter stomach is a result of losing fat for the majority of people (as most people wanting a flatter stomach are carrying excess fat). This is not achieved through a resistance based workout. It is achieved through a cardiovascular routine. Running, walking, sports, rowing, riding etc. A cardiovascular workout will burn a significant amount of fat in conjunction with a sound eating regime.
Many of these bogus products are based on the premise that it is possible to perform spot reduction (an old wives tail). The spot reduction myth is defined as choosing a specific section of the body to burn fat from. For example, if you carry extra fat around your belly, then the idea would be to perform situps to lose fat from the stomach area. The physiology of our bodies does not allow for this. There is zero scientific evidence that this is possible. Yet this belief is exploited by such companies time and time again.
I'd like to suggest reading an article I wrote regarding this topic: