[dools]

You can do this with BenkoBot, we just launched custom webhooks (although it's not in the interface yet). So you can receive a webhook and run some arbitrary javascript to transform it then send it on somewhere else:

http://www.benkobot.com/

Our main focus is on handling Trello notifications, and the Trellinator library I wrote is built in, our objective is to create more API wrappers over time to make it as simple as possible to deal with as many APIs as possible. You can see some example code here:

https://trello.com/b/IoHmhz5c/benkobot-community-board

You currently require a Trello account API key/token to sign up, but you can use it as you described to be a generic endpoint, transform however you want with JS then post the data onto another endpoint.