V-Phone is a memory stick with a headset adaptor that plugs into a USB port. It stores Vonage account information, thus making the Vonage account portable to any computer, including computers in airports or hotel lobbies.The device will cost $40 and unlimited calling will cost $35 per month per seat. More details over here.
The device, which has 256MB of memory, can also be used to store data files just like any other Flash memory sticks.
It is also loaded with audio-compression software to improve sound quality; when software is upgraded, the device upgrades itself behind the scenes during use and also has auto-troubleshooting capabilities.
Vonage to launch V-Phone

Vonage is going to launch a softphone device: