When I go to Voice Settings > Phones, I see an option to forward to my Google Chat account, what does this setting do?
Will it forward calls, texts, or voicemail? Would it work if I use a text only client such as Meebo?
When you have Google Chat open (such as in Gmail) it will "ring" your Google Chat when someone calls your GVoice number. (It's literally a phone ring sound.) You can then answer the call using the voice comm feature of GChat.
It's only going to work with the web GChat and if you've downloaded the special plugin.