I often get called upon by manufacturers to "review" a product with an outsiders view.  "Tell me why this product isn't selling" is the mission, even if it isn't said that way.  Many times, of course, they already know the answer and just need an outside authority to handle the nasty job of telling management that the R&D process missed the mark.

Sometimes the development was led by upper management who made the mistake of letting their own "gut feel" drive the development process.  In other cases,the problem stems from a process driven by the latest technology, not by customer needs.  Other times, however, especially if the development team and product managers are located overseas, they truly don't know why the product was a market failure.  They don't know the competition, local channels, or the end users, and just build the product to be successful in their own local market.

There is value in an outsiders point of view, particularly if the message is going to be a bitter pill.  Still, the real answer here is to get the development team the direction they need before the design is begun.  Almost always, a consultant's time is better spent helping to fix the specification or the process.