I'm not sure which thread is the best to post this in, but I was reading this thread, so I guess here works:

I was playing around with the Google Voice extension for google chrome (by google), and trying to figure out what they do to get new messages, since (like uvatbc mentioned) new messages appear to arrive fairly quickly (hoping to find some way to accomplish push messages).

This page shows what requests are being made by chrome, and is very helpful on deciphering the protocol that the google voice extension uses.

Two useful things I noticed:

Requests are made to: https://www.google.com/voice/b/0/request/messages/ to get a list of the text messages in an account. Each message has a unique ID, and each conversation has a separate unique id.

https://www.google.com/voice/b/0/request/unread/?b=0 returns the number of unread messages in all of the different folders.

I'm not sure how it logs in, etc, but hopefully this makes it easier to check for new text messages, since the current method is to scrape the mobile website, which presents some difficulties. This was the result of a few minutes of playing with the extension, so I am sure there is plenty more to learn about it.