More security for items exchange

I am reading on FB that theres some people doing deals for exchange emblems but when they do the first step and send first the emblem then the other manager disappear.

I think that would be gret to have a option not only to "send", but to agree a exchange, so if I choose this option there are some hours till I recive the other emblem, and then once recived we can use them, and if is a "smart guy" that wants to cheat or abuse of others just the emblem Ive sent come home again.