I've had the opportunity to go to several seminars and visit with quite a number of Dojos and have a fair aikido library, and all I have ever seen or come up with is Boken, Tanto, Jo and Bo.
As far as development of concentration, from somewhat an occidental point of view, I personally find firearm competition one of the most challenging. One is outside, its dusty, its too cold or too hot, as the wind blows your body will move. Points make a difference, and there is a time limit - you're trying to put an item as thick as a bic pen and maybe an inch or so long 600 meters down range into a what looks like a small black dot no bigger than the smiley face icon
used on this forum site. Or taking something the size of a pencil eraser and try to hit small metal targets, 10 each at 25, 50, 75 & 100 meters. Or hitting clay disks thrown at various speeds and angles within seconds of the start of their flight. One has to have no thought, an empty mind - Mu Shin - your Ki is flowing, there is a certain Zen feeling in place. No dusty, hot/cold, windy how did I do on my last shot, how did everyone else do on theirs, etc thoughts. One has to control their breathing and pull the trigger between heartbeats. And every time one pulls the trigger, it's a surprise, there is no anticipation otherwise one will compensate and flinch causing the barrel to move. That to me, is concentration.
I know there is bad press lately concerning firearms from the PC crowd, but none of mine have ever committed a crime. And over 60 Million US gun owners have never committed a crime with theirs. I've digressed please forgive me. Anyway, if you have the opportunity I highly recommend it. It's not as easy as it looks.
However, if your search leads you to Kyudo, Kendo, Jojutsu or Bojutsu then good luck. Just remember there are other less physical arts like the Way of the Brush - Shodo. Everything about shooting sports can be said about Shodo. There is no anticipation, no hesitancy, breathing is controlled, no thought, an empty mind, Ki is flowing and best yet
the PC crowd has not found out that the finest brushes are made from mouse whiskers yet, so it falls into the correct category
Yours in Aikihood