SIP VoIP adapters from Linksys are Sipura Based

Vonage connects with Linksys, Netgear on VoIP | CNET News.com
See Linksys Uses Sipura Technology in New Adaptors this is cool because you're able to use your cordless handset or wall phone. Still looking into this though the price $59 is not bad at all.

The Linksys devices will be available first. The $59 Linksys Phone Adapter plugs into Wi-Fi equipment, such as a router, and allows a consumer to connect a phone to the broadband connection to make VoIP calls. The $89 Broadband Router includes two phone ports, which would allow two phones to place VoIP calls at once.

The products, co-branded by Linksys and Vonage, will be available in retail stores and directly to Vonage customers, according to Malachy Moynihan, vice president of engineering and product marketing at Linksys. A division of Cisco Systems, Linksys is one of the top makers of Wi-Fi equipment. Moynihan added that by the end of the year, VoIP will be available on all new Linksys products, which will also work with VoIP service from other providers.

See PAP2 and RT31P2