I've been messing with FOBs in the basement. Paul sent me some as a giveaway and I promised I would give them an unbiased review. Out of respect for Elite, I'm not going to post a link to their website.
They do just what is advertised as long as your setup has clearance. Mine did from the get-go. I tried shooting groups with them but my second shot broke the first FOB. I then went to 3 spot and they shoot just as well as my target arrows. I have them on Beman ICS hunters.
I mistakenly hit my trigger on my release near full draw and sent an arrow into my heating duct. The arrow was fine and I found the FOB on the other side of the basement without a scratch. Not bad.
I will be using them next season for deer and I would try them for spots if they made some for my fat target arrows. I still like the way vanes look on an arrow but I like the idea of the arrow passing through an animal and having the FOB on the ground where the impact happened. I actually think these gizmo's have a place in our sport. I'm on the fence about 3D though for obvious reasons.
I almost forgot, Paul will help you with your setup to make sure you have the proper clearance. OH, only drop away rests can be use with these!