refs #4520 and #201
In my opinion the banner is quite ugly and outdated:

In addition it isn't maintained any more: https://github.com/jasny/jquery.smartbanner

But the library isn't needed:
iOS will show a system banner if <meta name="apple-itunes-app" content="app-id=737216887" /> is added (which already is): https://developer.apple.com/library/content/documentation/AppleApplications/Reference/SafariWebContent/PromotingAppswithAppBanners/PromotingAppswithAppBanners.html

And Chrome on Android is supporting a similar banner by adding the following to the manifest.json:

  "prefer_related_applications": true,
  "related_applications": [
    {
      "platform": "play",
      "id": "org.piwik.mobile2"
    }
  ]

https://developers.google.com/web/updates/2015/03/increasing-engagement-with-app-install-banners-in-chrome-for-android?hl=en#native (scroll down to Native app install banner)

Only difference: They are only shown on HTTPS and if "The user has visited your site twice over two separate days during the course of two weeks"