For Archimedes it was the bathtub. For Craig Walker, the eureka moment came during a routine airplane trip.

“Every time a cross country flight lands, what’s the first thing everyone does?” he asks. “They check their messages. I’d check my [cell phone] messages, then I’d dial into work. I might even call in for messages at home. And then I’d start the process of calling all those people back.

“I got sick of waiting for service providers,” he adds. “[I thought] I might as well do something myself.”

Walker figured that his problem was your problem, too, and that simple to use service with a low price tag would be a hit. Now, nine months later after lining up financing for his new venture, Walker is launching Grand Central (GC) Web-centric VoIP service. And he’s doing it right down the road in Fremont, CA from the last VoIP company he founded, DialPad, which was bought in 2005 by Yahoo.

GC promises that you’ll never have struggle through multiple voicemail boxes again. And that you’ll never have to buy new business cards because your telephone number — or email, for that matter — has changed. GC gives you one phone number and lets you route calls from up to six phone numbers to that number. You can also use the service to create local numbers for the convenience of out-of-town family or friends — although GC limits users to two accounts avoid system abuse.

The thing that sets this service apart is its utter simplicity. The interface is extremely straightforward and intuitive. It takes about a minute to sign up on the site and you can start taking calls. What can’t be configured online — your voicemail message to callers, for example — is set up through a phone call. But in keeping with the elegant simplicity of the design, it’s a phone call that GC makes to you, so you don’t have to deal with menus or key sequences. You can get to your grand Central voicemail by phone, email or from the Grand Central website. The system integrates with Microsoft Outlook address books.

But although GC is simple to use, it’s extremely powerful and raises the bar for flexibility.

For example, it allows you to filter calls as they come into your GC number, just like an answering machine, provides both visual and audio caller ID and lets you block unwanted callers and junk calls.

You can listen to the message and decide to take the call right then. From the website, you can store voicemail as long as you want, sort messages by any field, and quickly find messages even years later. One of the cleverest features is a ’notes’ field that lets you annotate messages for later reference. You can also answer a voicemail with an email — GC even fills in a standard reply so all you have to do is hit ’send.’ And, Walker stresses that you always stay in control of your messages even when you forward them. If you delete a message, the link dies. Even if it is forwarded the message is gone.

GC also brings a new level of personalization to communications. You can create different greetings for different groups of callers — for example, business callers, friends and family. People who do business or have family overseas can create messages in different languages. And if that’s not personal enough, you can create special greetings for individual callers.

Why build around the phone number instead of, say, an email address or a SIP address? Quite simply, it’s familiar. Walker points to the 600 million phone numbers in the US already. It’s going to take a long time for anything else to displace that. But in the long run he sees unifying all communications — not just voice — as part of the fledgling company’s mission. “The same problem that exists with phones exists with email and IM,” he adds.

In fact, GC has already made a start with email. Users can have email sent to grandcentral.com using their phone number — e.g. 4151234567@grandcentral.com — and messages will be delivered to the email account they used to register for the service.

But regardless of what the future holds, Walkers thinks GC is well positioned for it. “Even if you unify around an email address, you have the same call requirements,” he says. “Regardless of what the mechanism to initiate the original call is, the call features you need are still the same.”