Want to play with building Twitter apps on Tropo? Source code for 5 simple apps
blog.tropo.com
blog.tropo.com
Though keep in mind, Voxeo's been around for a while. It's probably more accurate to say Twilio is a competitor to them.
1) Tropo Scripting, where the app is hosted in the Tropo cloud (similar how Google App Engine works) and is written in PHP, python, Ruby, Groovy or JavaScript; or
2) Tropo WebAPI where you run the app on your server and communicate with Tropo via a RESTful API using JSON. The app can obviously be written in any language you want since it's on your server and can use all available libraries. To help developers get started with the WebAPI, we've made available libraries for Ruby, PHP, python, C# and Node.js. (Available at http://github.com/tropo )
And yes, Voxeo has been around since 1999 and is the largest hosting provider in the VoiceXML/CCXML space.
I actually had a (brief) twitter conversation with the CEO of Voxeo asking about standardizations. I like CCXML OK but really, it doesn't serve the same need as Tropo/Twilio. I'd like to see a more 'push' oriented standard get developed.
Actually, I just looked, you responded on twitter too. So, any chance of trying to get a 'push' style API standardized? :)