No experience with it, but I struggle to imagine it being useful where the viewed person is a programmer. A day is split between, what, a browser and a terminal emulator? And an IDE if used?

I agree but this might be already useful. The biggest challenge for most when they work from home is lacking social pressure leading to procrastination. When I read about Tandem's take on this, I thought that’s a smart, subtle solution. You could still game the system by just using your phone but still: Any cheating results in odd behavior on Tandem and probably to more discipline. Maybe I am wrong but I need just people who tried Tandem and share their experiences.

Isn't this really an incentive problem? I find it hard to believe that snoopware will foster a high trust environment.

The real usefulness that I’ve found has been in having a pointer during screen share, and being able to more fluidly hop in an out of voice calls (think discord).