It is a great way for someone to earn money!
The only thing you need to know about doing crunches is not to do too much in one go, use a towel instead of all of those gadgets:
Spread out the towel and lie on it with the top edge just level with the top of your head. Crunch in the usual manner but hold on to the corner of the towel. Perfect head support wihthout reducing the effectiveness of the crunch.
Have fun without giving in to odd commercials!