Maybe I am misunderstanding what you are going for here, but the Scrape.Post action is not going to help you with this in any way. Post is for sending information from VoxCommando to a web service and getting a response back.
You can send events and actions from the Pi using our extensive api options:
http://voxcommando.com/mediawiki/index.php?title=API_Application_Programming_InterfaceThat is not going to help you get audio to VoxCommando though, so you would need to have a program on the Pi doing speech to text conversion which is probably not likely.
One possible option is to install Android on a Pi and then use VoxWav but I'm not sure what kind of audio input options you would have in that situation since Android does not support USB microphones as far as I know.
Another possibility would be for someone to write a program similar to VoxWav for Linux which could be run on a Pi but that person is not likely to be me, or at least not any time soon. If anyone is interested (and serious about it) I can provide information on how to talk to the TcpMic plugin in order to send audio data to it, the same way that VoxWav does.
Another option for a programmer if it is easier, is to record a wav and save it to the wav directory watcher folder:
http://voxcommando.com/mediawiki/index.php?title=Options#Directory_Watcher