The long-rumored Google Project Fi cellular service became a reality this week. It promises cheaper smartphone service ($30 per month for 1GB), and uses Wi-Fi networks when possible to offload the voice and data usage from congested, expensive cellular networks -- technology already pioneered by T-Mobile and available from several carriers on numerous widely used smartphones, such as the Samsung Galaxy S6 and Apple iPhone 6.

But Google brings something to the equation beyond its brand and encouragement of affordable cellular service, and I believe it holds significant promise: cloud-based phone numbers.

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Anyone who works in multiple locations knows the frustration of a traditional landline -- each location has a separate number, and it's very difficult to manage the flow of calls from one number to the next, even with services like Google Voice.

A cellphone seems like the answer, except you must then use the same number for business and personal contacts, which also means your phone never stops ringing. Plus, your cell number quickly becomes a target for spam calls -- so much so that FTC officials advise you not give businesses your personal cell number.

For companies, this number commingling makes it too easy for key business contacts to walk out the door with an employee. Several VoIP services such as Google Voice, Line2, Flyp, and Citrix Convoi promise to add a second line to your smartphone to solve this issue, but in my testing they work poorly.

In some parts of the world, cellphones have two SIM slots. That way, you can have separate work and home phone numbers, or service from different carriers (for coverage issues or if you work in multiple countries), or a "real" number and a "burner" number for marketers and salespeople (as many of us do with email addresses). However, they are not available in the United States.

In Project Fi, Google says its use of a cloud-based number will let other devices (such as tablets) make and take calls. That means the cellphone number is no longer tied to the specific cellphone, but available to multiple devices. That could help solve the "many locations, one number" issue.

If Google extends the concept to allow multiple phone numbers, it could help solve the "one phone, multiple numbers" need as well.

Google Voice does neither of these today. For the "many locations, one number" issue, Google Voice forwards calls among several actual phone lines. For the "one phone, multiple numbers" need, Google Voice lets you initiate a call from its number on your device, then patch it into your actual phone line, which is operationally awkward. It lets you do something similar for placing calls from a smartphone. The idea is sound, but the execution is terrible.

Likewise, Apple's Continuity feature in OS X Yosemite and iOS 8 sounds like it should solve the "many locations, one number" issue, since it lets Macs and iPads make and take calls. But they need your iPhone to be in Wi-Fi range to handle the calls, which are still made on the iPhone, with the other devices acting as handset extensions.

Project Fi, as its name suggests, is not a product but a public test. That's why it works only with Google's own Nexus 6, a behemoth of a smartphone that has garnered mixed reviews. Google Voice is also a test, one that has evolved little in the six years since Google bought its creator Grand Central.

Google routinely launches tests that it abandons or leaves in limbo. Google Voice's long stagnation is a big reason I'm not holding my breath for Project Fi to deliver a solid, modern approach to telephony for a mobile, multipoint, commingled world.

But it could be. Maybe Google will make this challenge seriously this time.