This is purely a stop-gap measure until they release a proper API.
Dialing a number is simple
$gv = new GoogleVoice('<username>', '<password>');
$gv->call($your_phone_number, $their_phone_number);
Sending a text is easy
$gv->sms($sometext, $their_phone_number);
This code is released under the MIT Open Source License. Feel free to do whatever you want with it.