There are so many Good Odoo Mobile related Modules around, I will be updating them here, you can let me know if you like them ,
you can click on the link and find out more about them there,
- (OCA) Web Widget One2Many Product Picker : Look at the pictures. It is not too difficult to understand what it can do, a really awesome made by the OCA fellows.
- (OCA) PWA : [ FOC ] Progressive Web App , it is a module where when installed it, it can make our Odoo to act like a Mobile APP, if you know how to link up firebase or make use of the service worker, you can do pretty much most if the mobile app can do.