A few issues I see. First is what does it do when you come across a no-haggle dealership? Next is does this negotiate the value of your trade-in? Finally, the initial negotiation up front on the sale price (and trade-in value if applicable) is only the first hurdle. When you have to come in and sign the paperwork and get your keys, that's when a lot of dealerships really try to tighten the screws. Oh you need an extra warranty! Or you need paint protection and nitrogen filled tires! How about that one-time fee for lifetime oil changes and maintenance?