Our own AgentP offers a service, detailed here on Litopia. Click Downloads to view, and darn good, too; expect a friendly skewering.
A smaller service, I have not tested it out, is available here: https://www.writersandartists.co.uk/writers/services/agony-agent
A smaller service, I have not tested it out, is available here: https://www.writersandartists.co.uk/writers/services/agony-agent
