I prefer guardian over this.
(note that I don't have WotC,idk if it was changed in that) from my experiments, it seems this activated if you don't take any non-movement actions, meaning a team of people with this could just end their turn ever round without moving and automatically be in overwatch. This would be extremely useful vs rulers (though still need to test that effectiveness in the field, but could be extremely powerful vs them as it would be effectively 6 attacks /one of their turns)
Essentially lets you double-move and Overwatch every turn, but if you do anything but double move you don't get the benefit. I see this as being very useful in cover missions, but the power of Guardian cannot be denied.