The most known ones are Monetha and UTRUST. The major difference is on how the solution is catered; we have considered both buyers and sellers throughout the whole process. We have an escrow solution unlike Monetha and a clear implementation decisions related to hold periods, recourse and risk management (e.g. for various forms of established reputation system vulnerabilities like Sybil attacks, ballot stuffing, etc.) unlike UTRUST. To also add Verify has a crucial differentiator, it is a reputation protocol that governs participation in the network, applications can be built on top of it. One application is the Verify Payments which is described in the whitepaper.
We have posted a brief explanation on how we are different form Monetha and UTRUST here: https://medium.com/@verify.as/verify-the-solution-to-the-trust-problem-in-crypto-commerce-2cbaefed15e0
We are also working on the initial version of our API here https://docs.verify.as