Filipe,

In the WebPatterns you can use the action CurrentOS to identify the device OS

CurrentOS is currently not done to mobile , but its very easily to make it work on offline, just open  a clone of webpatterns, enter the CurrentOS action, and copy paste it into a client action, since it's all ifs and assigns, it will convert all of them to offline ones.

Silk team is already aware of this and will come in a future version (if it's not already, I haven't really seen latest release notes) but you can do this workaround for now.

You can also do something like this in a Javascript node in a mobile app:

Code: 

var isMobile = { 
   Android: function() { 
      return navigator.userAgent.match(/Android/i); 
   }, iOS: function() { 
      return navigator.userAgent.match(/iPhone|iPad|iPod/i); 
   } 
}; 
if(isMobile.Android()) { 
   // Do stuff 
} else if(isMobile.iOS()) { 
   // Do stuff 
}