That's actually more like the theory behind guilt-free play. With the Unschedule, you mark any completely unavoidable block of time (meetings, meals, sleep etc)

That's actually more like the theory behind guilt-free play. With the Unschedule, you mark any completely unavoidable block of time (meetings, meals, sleep etc). Whenever you happened to have done a half-hour of completely focused work, you mark it. This lets you a) spot patterns in when you work best (e.g. I seem to do my most focused work on a Tuesday morning for no apparent reason), and it gets you thinking "It's 2pm, I have a meeting at 3, I could get this small bit of work done". I would also recommend Getting Things Done; even if you don't subscribe to the entire method, there are bits that gel quite nicely with the Now Habit; the bit about just starting which this article also touches on falls nicely into place with GTD's "next action" workflow.