** Apologies if this in the wrong section as Im new to this forum and was unsure where to post.**

My partners and I have begun a new start up and are developing a website to post ads/classifieds primarily through the website. However, at the time of launch we also need to have an App for Android and iTunes available for our users. The reason being is that instant ad/classified post notifications are a key to this project.

So to clarify, a user may post an ad/classified on either the website or mobile app under a certain topic and individuals who are subscribed to that topic should get an alert or notification via app, email or text of the recent post.

My question is this: what service, system or technique would you recommend to create a website and mobile app that syncs and integrated seamlessly? I have heard of Heroku which is a cloud based database but it seems like it is only for mobile apps and not web server? How would you go about creating this project?

Additional info: We are likely going to use a custom developed Wordpress theme, but this is not mandatory if it creates an integration issue. Also, we plan on having a massive amount of traffic after launch and need a server or service capable of handling such volume.

Thanks to all in advance!!!