I would be interested at doing this with low fees, but I fear that I do not have enough trust in the community yet.
onchain.io is trustless because we are creating genuine multi sig contracts. Only if 2 participants agree can the Bitcoins be spent. As an escrow agent you would not have access to the funds so participants only need to trust that you will mediate correctly.
Here's a presentation about how it all works for escrow.
https://docs.google.com/presentation/d/1xh8VgjYtTZr6lZY3hJirrPiFUX9yJHx3ga3Ac-lDtO4/edit?usp=sharing