Simon Telephonics Google Voice Gateway: Create a standard SIP connection to Google Voice

The Google Voice Gateway connects your Google Voice number to any SIP device or URI (incoming calls only). The service adds these features on top of the features you already get from Google Voice.

Log in to sign up or modify your Gateway connection:
Sign in with Google

Note: This service requires a full Google account--either a GMail or a Google Apps account (with GMail service).