The timesheet is the screenshot history
A freelance analyst bills by the hour. A new client wants proof of work and proposes the usual answer: a monitoring agent on the analyst's laptop, screenshotting every ten minutes, uploading to a vendor.
The analyst works on a display in a container instead, and offers something better. A cron entry GETs /api/v1/display/screenshot every ten minutes during the engagement. The service keeps each one, addressable by timestamp. The client gets a permission group that allows that display and nothing else.
At invoice time, /api/v1/display/screenshots lists every capture for the month. The client pulls /screenshot/1723712400 and sees the spreadsheet mid-edit at 14:20 on the 15th.
No spyware on a personal machine, no vendor holding the images, no dispute. Proof of work is a list of timestamps, on a machine you control, that the client can read.
Proof of work is a list of timestamps, on a machine you control, that the client can read.