I’m wondering if this is achievable with stock ERPNext.
There is a QR code placed in office/warehouse entrance. Each staff entering the workplace must first log into the mobile app, then scan the QR code.
Every scan time will be recorded. ERPNext will base on the scan sequence to determine if it is start-time, out-to-lunch-time and so on, and these will be summed as today’s total work hours.
Of course , you can use erpnext api inside your mobile app to send data to the attendance database. however you should consider change your method because your employees can take a picture of the QR code otherwise you have to change it many times during the day which is not easy .