I appreciate the comment, but although focus drift is the fundamental problem for task completion, I don't think a task manager app solves focus drifting problem at its core.

I mean, focus drift can happen anytime, say you go to a room and forget why you came there (or) say you go to the bathroom and start brushing the teeth unconsciously even if you hadn't come to the bathroom for that; we will not be using task manager apps for that.

I think only a sensor based approach which gets all the data which our eyes get as Abishek mentioned in other comment could address the problem of the focus drift.