A new Web API for EDI claims is the ClearEHR Health Insurance Claims API - this tool doesn't map the data, it replaces the need for any EDI data generation on the developer end as the API handles all of the EDI creation, and parsing the EDI responses. And it is free to use.
https://837-edi.clearehr.com
JSON encoded responses, and web based (RESTful) make it ideal for web development.
Disclaimer: I am a developer for ClearEHR