If you are trying to shift traffic from existing website to app use interstitial blocking pages. While somewhat annoying for users that just want to view content on the web they are very effective at directing traffic to apps. They're far more effective than the default iOS smart banners that are easily ignored. We found this for both iPhone & iPad use cases at Diapers.com (I also saw similar data from zappos) also once users dismiss interstitials or smart banner adding contextual links like "view XXXX page in the app" can prompt users when they're more committed as opposed to on first view.