Ok, so is there another convention for sending json data?

My use-case is, I want to send a notification to a specific user say "that item you have been watching is now available" - and when the click on it, the app opens, and they see a screen with price, currency, etc - a domain model. 

Is 'push' the right/normal way to do that? Or is there another convention?

Or would it be a combination of push, then do a rest request?