usually, 2d barcode are used for input, not for output.
Probably we should make it two ways.

Idea: you scan a barcode, your device connect to an url (OR computer or id) provided in that barcode, then, your device provide your data or upload something.

不只可以用 GPS, Cell ID, Blue Tooth, NFC 來偵測位置
也可以用 accelerometer 來預測目前在幹嘛 進而推測位置

『更可以用聲音』推測目前在哪裡(ex: Bar, Bus, Street, 7-11, etc)