Google currently supports several ways to encrypt the voice payload (the RTP stream) from the client to the Google servers.
Google supports:
RTP over SSL/TCP (TCP over TLS)
and
Google Talk supports SRTP for media encryption, which supports the crypto-suites of AES_CM_128_HMAC_SHA1_32 and AES_CM_128_HMAC_SHA1_80 as described in RFC 3711.
I saw these protocols listed in the data sheet for the Obi110, when can we expect to see them implemented? Unencrypted UDP based RTP streams are just too easy to capture and decode, please get these features released soon.