Went for a 40 minute treadmill walk.
Earned around 4800 steps, 0 intensity minutes.
My HR was bouncing around 80-95, but had one spike (probably inaccurate) to 134 (when I started on the treadmill at a slow speed).
Started around 2.5 mph and worked up to 3.3 by the end, 0 incline with 3% by the end.
The IM meter started flashing a couple of times, but clearly not enough activity to kick it into counting.
Conclusion: a walk may or may not kick in the IM count. I successfully had it count on an outside walk with some significant hills - distance of 1 mi, time of about 15 minutes. A 40 minute walk on the treadmill didn't work this time.
More and final thoughts for now: http://www.midpackgear.com/2015/11/vivosmart-hr-review-more-about.html