I would like to ask if anyone knows references or documents for customizing SAP CRM Sales 2.1 by modifying the client side source code (in my case: iOS platform). I am referring to type of  customization like adding or removing fields

I have read this whitepaper http://scn.sap.com/docs/DOC-32984#comment-333958 which covers the server-side (sap crm) customization