With the patch 5.4.2, something very important has happened: You can send Bound on Account items cross servers. It is a very big improvement. Once upon a time, I had to move a character with heirlooms and other bound on account items if I wanted to share those with my other characters. I eventually had to switch faction. That meant 40 euros just to move some virtual gold and items from point A to point B.
That can now be achieved just by sending the bound on account item from one character to another. You just have to send to name.of.character(hyphen)name.of.server. You don’t need to use hyphen between the words if the server’s name is composed of more than one word.
For example, if my Alliance rogue from Sporeggar wants to send something to her alter-ego Horde (Sheket) on Defias Brotherhood, she just has to send the item to: sheket-Defias Brotherhood
It doesn’t matter if it is same or opposite faction. If the item is faction defined, like the PvP trinket, it will change from Alliance to Horde or the opposite. Don’t worry about that.
You can send every bound on account equipement, also the items you can find around Pandaria, the ones you can make yourself (like the staves made by a scribe) or the items you can make with archeology. There are no limit.
You cannot send gold or other items, though. Just the bound on account items. One could say that only now, the bound on account items really are bound on account. Before now, you had to pay real money to move a characters with the items you wanted to send around.