the question is WHY would anyone in his right mind do that? it is literary "masochistware" as stompix said!

if you like the idea of it then do it on your own. how? just use two keys, encrypt whatever you want with them and then hold one yourself and hand another one to another person you trust or simply store it elsewhere. you don't have to use a third party to encrypt-decrypt your data. it is not some secret technology that they are using, it is open source and for everyone to use.
it can simply be a long password (60 char long) and you store 30 character of it and the other person the other 30 and encrypt your data using one of those password managers (trucrypt,...)