Good news for VoIP consumers: A seldom-used, but major feature of Internet phone service just got a big boost: the ability to take your phone with you on the road, to make and take calls from the same number at the same low price. Good news for VoIP consumers: A seldom-used, but major feature of Internet phone service just got a big boost: the ability to take your phone with you on the road, to make and take calls from the same number at the same low price.

The problem with this idea is that you usually have to take your adapter on the road with you to hook up a regular phone to the Internet, or install your VoIP service provider's software on any computer you want to use - typically limiting your options to the use of your own laptop computer.

Vonage has come to the rescue with a solution that will help users realize the full potential of VoIP: the V-Phone. The V-Phone is a keychain device - actually an ordinary USB drive with Vonage software and your user ID pre-loaded - that you can plug into a USB port on any Windows-based computer with broadband access, for instant Internet phone service.

The device is easy to use: you plug it into a USB port and the software loads automatically, displaying a small window with a number pad that resembles the keys on a regular phone. Online authentication between the keychain and Vonage's servers typically takes from 30 to 90 seconds to complete.

Importantly, the V-Phone does not load any applications to the computer's hard drive during setup, so you don't have to worry about leaving "debris" on other people's computers when you're finished. Simply unplug the device and all icons disappear, along with any trace that you were ever there.

The V-Phone comes with a jack for plugging in standard cell phone earplugs, a set of which are included in the package from Vonage. This has a couple of advantages: you don't need to locate the separate sound and audio ports on the computer, and with desktop PCs, you don't need to unplug the speakers to plug in your earphones.

The unit sells for $40, which doesn't include the $10 activation fee and $10 for shipping. It's available for purchase online from Vonage now, and will be sold by major retailers in September with a $40 rebate.

Calling plans are the same as for any normal Vonage account: $15 per month for 500 minutes, $25 for unlimited residential use and $35 for business service.

One important point to note is that the device comes programmed with its own number and calling plan. There is no option offered for having an adapter and V-phone programmed with the same number. This means that if you choose to port your existing home Vonage number to a V-Phone, your home will be without service every time you take the device on the road.

This makes it most practical for businesses and other users willing to add an additional Vonage account, rather than transfer an existing number to the V-Phone.

This novel product takes mobile Internet-based phone usage to another level. That's great news for Vonage which, as the industry leader, is in the enviable position of having to fight off rivals who are cutting prices and even giving away phones for free in attempt to gain market share.

The bad news for Vonage is that this device is a no-brainer - it's surprising that no service provider offered it previously. The likelihood of Vonage getting a patent on the technology is not great, and it's certain that rivals will be offering competing products soon.

That competition could be even better news for consumers.