I'm not sure if you have to open the app up and look, or if it's like push notifications - that would be really annoying.
Google notifies you if stores selling things you've been looking at online. This seems to invasive to me.
Google Now Shows Nearby Stores with Products You've Searched
Apologies if the link doesn't work, I'm on my phone.
That does sound annoying. Amazon e-mails me about things I've been looking at on Amazon.com, which I also find annoying, but a lot less annoying. If I buy something, Amazon doesn't e-mail me about that thing, but a few months ago I was looking at a bunch of things, considering buying them, but my girlfriend bought them for me for my birthday (on her Amazon account, of course), so obviously I didn't end up buying them, but Amazon has been e-mailing me about them for like two months now, oblivious that I already own everything they're nagging me to buy. The idea that an app would send me pop notifications like that is especially annoying!