Like Heart Mail...
When either Pokemon is equipped with this item, Trick fails.
Mail with a heart pattern. Allows you to write a message to yourself or a friend.
Besides equipping it on a Pokemon in battle, you should be able to attach it to Pokemon when trading/gifting, and include a silly message (yes, pointless, but I would totally do it for shits and giggles). The message can be sent by mod or trade approver.
Seriously, this item has competitive viability. Switch in on someone using Trick with a Choice item while holding Mail and they will be stuck using Trick unless they switch.
Edit: Various Mails found here: http://bulbapedia.bulbagarden.net/wiki/Mail