Ya know, I watched that video seems like 100 times (with the volume turned down...anoying sound from that bow) anyway it may just be a bad video but I could swear that arrow is ever so slightly moving around. You can see it just before the arrow is fired. If that's tha case I wounder if it's enough to cause accuracy problems.
I think both the weight of the arrows and the weight of the rest would be much more than most people would care for. After all magnets are heavy and I bet the one in the rest is a pretty good sized one to compensate for the small one in the arrow.
Also the arrow tip needs to be close to the rest. This would make me nervous having a fixed broadhead behind my hand just floating around
I know the rest completely surrounds the arrow but it'a a pretty big opening.
Other than that it's a pretty neat idea.