The tricky part is the client wants to keep the product a "secret". They don't want to create the product page as the teaser URL, since the optimized URL for the new product would reveal the new product itself.

I agree with your approach, but I the trick here is going to be optimizing a /coming-soon page that then redirects to the new product page a week or two before the launch.

Within the context of a physical product launch what are some ideas around creating a /coming-soon page that "teases" the launch. Ideally I'd like to optimize a page around the product, but the client wants to try build consumer anticipation without giving too many details away. Any thoughts?