And the second thing would be just to improve the lag time between grasping the handle and the deactivation of the magnet, so I can just lean down and casually grab it, instead of having to hold it for a second before bringing it up. The more magic, the better.
Still, this is pretty awesome!
Just try with a magnet on your fridge door. It's much easier to slide it around than it is to pull it away.
A Pro Mini draws a tiny amount of power, I'm talking tens of milliamps- he could leave this hammer somewhere for weeks probably without the batteries dying, with the occasional passerby trying and failing to pick it up. To manage that with the magnet running constantly would be impossible.