There is no conference room phone product that directly connects to Google Voice, but you can attach any analog Soundstation or similar device to the analog RJ-11 phone jack on an OBi 200//202.
If it's just a small room or office, the Poly 2182 is a great, full-duplex speakerphone, and it can be setup to directly connect to Google Voice.
Note that my remarks refer to the consumer version of Google Voice. If you are a G Suite customer, then OBiTALK devices won't work. However, Poly's new VVX 150,250, 350 and 450 IP speakerphones will work.