We recommend that you download the model once, save it and bundle it with the app. You retrieve the model in JSON format from the BigML API and you can reify it into a function or method of your choice locally. Check these bindings for iOS or Switch for more info.
You can either do this when you are building the app or (even better) by downloading the model either from BigML or your own server dynamically at runtime so you can alter the behavior of your app without bundling it again.
Another possibility is to download the actionable model in Objective-C. To do so, simply navigate to the model view, select the model you wish to save, and click the Download Actionable Model menu option:
Later, you can export the model rules in the programming language you prefer, Objective-C in this case.
BigML also offers actionable clusters and actionable anomalies. You can download them from the right view (either clusters or anomalies) by clicking the same menu option as indicated above.