Implementing Multi-Sig Escrow?
You basically got it.
create 2-of-3 multisig addresses (meaning needing two out of three signatures)
1 is for the buyer, 1 is for the seller, and 1 is for the mediator


buyer sends money to the multisig address, commiting the funds to the transaction
if the transaction goes well, buyer sends a signed transaction
spending the multisig output to the seller and sends the transaction
to the seller, the seller signs the tx and broadcasts it
if buyer is unhappy he/she can try to work out the matter with the
seller till they agree on any split of the money, it would involve
same steps as in (2) except now the money is divided (any
percentage) between the buyer and the seller
if the buyer and seller can't work things out, the mediator steps in
and after a decision is made, the money is split between the three
addresses (buyer, seller, fee for mediator)


So those are the conceptual steps to implement the scheme