Sage CRM offers native iOS and Android mobile CRM apps. The apps allow you to view contacts, opportunities, notes and customer information with or without internet access. The snag is that these apps are fixed in scope and can not be extended to include new custom entities or features.
This is where the mobile optimised theme for Sage CRM becomes one of it most useful features for customers. The optimised themes allow online access to Sage CRM using just about any mobile device. The themes present a subset of Sage CRM's screens in a form suitable for the device and screen size being used to access the data. These mobile optimised screens require internet access but they can be extended to include new entities, fields and structures.

The mechanism for extending the mobile optimised themes is code-less. There are no scripts to write and it is all done by using the inbuilt system action 'RunBlock'.
RunBlock can also be used to build addition screens for the main Desktop interface. Over the last few years there have been several articles written that together build a very good pictture of how to carry out customizations using RunBlock. Below are just a selection of these.
RunBlock Fundamentals
Using RunBlock to Build New Mobile Screens (iPhone/Android and Tablet)
Note: The articles below refer to building iPhone screens but the same method is used for building screens for the Android and Tablet themes.