Much of the business logic is written using ABAP Web Dynpro components on server side which are currently accessed using iViews for a SAP Portal.
Is there a way to access these Web Dynpro components from iOS mobile applications (iPhone/iPad) to leverage the existing business logic server side?
Web Dynpros are not designed to be used in a mobile enviroment. Web Dynpro has a relatively large footprint on both transmission and local processing - not ideal for mobile environments. Besides, the UI is optimized for mouse-and-keyboard use (e. g. small buttons), not touch interfaces.
If you have decoupled the user interface from the business logic (as you should have), it should be relatively straightforward to just add another UI layer on top of the business logic. Be aware that you'll probably have to re-think the UI composition because the way people use data and functions change drastically when you exchange a stationary PC or a laptop for a mobile device.