simple REST server?

I've got a project where I am integrating Drupal with a third party service (a video upload/transcode/hosting provider, kind of a white-label YouTube: twistage.com)... when something updates at that service they want to ping my server @ a URL I designate with some simple key/value pairs, and I want to act on that ping.

Services seems like a perfect fit, except: a) XMLRPC and AMFPHP seem to be the only servers pre-written; and b) I haven't grokked the server part of the services equation to author what seems like a super-simple server - one that only responds to $_REQUEST variables.

I can do it on a normal Drupal node (the 3rd party service doesn't expect a response, so it will ignore that I am sending it back HTML)... I'll just code some PHP to process the $_REQUEST and do my actions...

However, I can't help but think that Services seems like a more elegant solution. If there was a screencast or doc example on servers as clear as the ones for services, I think I could write it, but alas, my Drupal skills are nascent and the server example doesn't seem self-evident to me at this point.

I thought I'd post here to see if anyone else had ideas, input or shares my plight. It is not meant as one of those annoying Open Source "why doesn't your software do X" type posts. I appreciate all your work, and am only here because as I understand it, it would be the most elegant solution if I understood the server part enough.

Thanks