my cousin plays for HK baseball team and i see everyone on his team using these. The ones they use are from Japan called Phiten something and they all tell me that after a long day of baseball it actually helps relax their muscles. I know they sell these in hk for 300-400$hkd for a bracelet and 1000-2000$hkd for a necklace. Pretty ridiculous if you ask me.
http://www.phitenusa.com/