Right after the Macworld announcement of the iPhone, many had hoped that the Apple iPhone might be able to make voice calls via Wi-Fi hot spots. That didn’t come to pass, and now it’s clear why it didn’t. However, T-mobile is making it happen in the U.S. with their HotSpot@Home service, according to Business Week on Thursday.

There are some mobile phones that will make calls via WiFi, but "such phones have never been particularly user-friendly," wrote Stephen Wildstrom. Now, however, "T-Mobile has come up with a fresh approach that’s practical, and nearly effortless to use." It’s called the T-mobile HotSpot@Home.

It appears that T-mobile, a cell phone carrier that lags behind the competition in conventional cell phone coverage, has figured out how to leverage one of their strengths. T-mobile has invested heavily in Wi-Fi hot spots in airports, Starbucks and Borders and has figured out how to exploit that network -- in addition to home Wi-Fi networks.

In the past, the problem of switching seamless between a Wi-Fi call and cell call has been technical. There has not been a simple way to switch between the two networks. "Taking advantage of Wi-Fi required connecting manually to a network and using voice over Internet protocol (VoIP) software that did not let you make or receive calls using your handset’s regular phone number," Mr. Wildstrom wrote. "No wonder Wi-Fi capabilities ended up being used almost exclusively for data." Such is the case with the Apple iPhone.

However, T-Mobile has devised an automated, transparent solution. It requires the use of a Linksys or D-link wireless router (supplied by T-mobile for US$50 after a rebate) that supports the "Wi-Fi Protected Setup" standard. Using that system, your T-mobile phone will connect to the network in your house, or to one outside, when the phone is in range.

"Equally important," the author pointed out, "your phone behaves exactly as if it is on T-Mobile’s regular wireless network, even though you are connected through Wi-Fi. Instead of a signal being sent to your handset from a tower, the call travels over the Web to your home network, which then generates a ring signal. If you happen to be on a call when you move in or out of Wi-Fi coverage, you switch networks without dropping the connection."

There is just one inconvenience. You’ll have to buy a T-mobile supplied cell phone that has the technology built-in, and the current choices aren’t so good. Right now, it’s the Nokia 6086 and Samsung T409. However, T-mobile said new phones will be added t the list.

One has to wonder why Apple didn’t do this with the iPhone. It turns out that the technology use is called "Unlicensed Mobile Access." Unfortunately, AT&T, a "technological laggard," according to BW, hasn’t implemented it.

Perhaps, pushed by Apple, AT&T will now proceed, and iPhone customers will be able to achieve that dream of seamlessly making mobile calls from Wi-Fi spots. The question is whether the first generation iPhone has the hardware necessary to operate in that mode should AT&T chose to implement the technology.