What does 装卸 mean here?
购物助手(shopping helper) is the topic
一个可随意装卸的无线电脑工具。'a wireless computer tool (device) that can be mounted and dismounted at will.'  is the comment on the topic. It explains what 购物助手 is.


Since 购物助手 is a device, 装卸(mount/dismount) here refers to the mounting and dismounting of the unit itself--  nothing to do with data upload and download.

By the way: 


'Data upload and download' in Chinese would be '数据(data)上传(up load)和下载(down load)'.  
Not '数据(data)装上(load up)和卸下(unload)'