HI Amey
Best advice is to work through the free online MOOC on this topic at http://open.sap.com/courses/mobile2. It explains all the basics about offline SAPUI5 apps that you need to get started. Although the examples use HCPms the approach, considerrations, and coding are pretty much identical on SMP as is explained in the course itself.
One of the basic principles is that an offline app should always act as an offline app. So it may make more sense to consider creating a separate app for online desktop users.
Good luck
Jocelyn