Is there a working and reliable escrow that works on the blockchain?

If there isn't would you use it if I made one? Image creating escrow smart contacts as per your conditions, neither seller nor buyer wouldn't need to trust each other as well as to pay a fee to third-party escrow service providers (of course creating a smart contract costs money but when chosen the right smart contracts platform you could lower it to a minimum).

Or, kindly recommend one you already are using. Thanks.