Bitmarkets instead uses two party escrow directly between buyer and seller with no third party. In our system the buyer locks 2x the price of the item and seller locks 1x the price of the item into a transaction and both have to agree how to unlock for payment or refund. This ensures both parties have an economic incentive to complete the transaction without the need for a trusted 3rd party.
The Bitmessage network is used for posts and buyer/seller communication and the Bitcoin network is used for payments. The app connects to those networks using the location hiding Tor network.