Something like this would be useful if it were a product-specific opt-in at the time of search. However, they are sacrificing utility for the ability to push more ads.
Companies do not seem to be seriously considering the negative reaction that useless private-based notifications provoke. I am a mild-mannered person, but I get very pissed off when I am interrupted by a service that pushes me something that I do not want or need based on a poor interpretation on my behavior. A non-personalized useless push is far more forgivable than a failed-personalized useless push. Any location-based notification that is not spot on is spam.
What's the deal, mk? You don't want to find Hot Singles Near You?
It's amazing what a point of sales system, a few databases and an algorithm could potentially do. Unfortunately for Google, I don't think they have a lead in the POS infrastructure that Square or PaySimple has. It seems so approximate.