I posted about people using rubber ball instead of a chair. I found a chair that require you t balance. It is called "Swopper". Other than the fact it cost $550 to $1000, it looks like a good office chair.
Tetsuro Watanabe 
ロッキーおしょう 
ウチクラ ケンイチ 
中村祐美子 
Junya Suzuki 
Lupin 
あさこ 
さわ 
落語好きプロコーチ 砂村よしお 
木曽町田中屋豆腐 
SETSUKO