The technology's advocates say that as long as people are paying for high- speed Wi-Fi access in their homes, they should be able to use it as a conduit for inexpensive calls and an alternative to traditional phone service.

But in a twist that raises some tricky ethical and legal questions, the phones can also be used on the go, piggybacking on whatever access points happen to be open and available, like that of Schaffer.

Schaffer, a retired business teacher, seemed affably cautious about the idea of having his bandwidth borrowed.

"If you're a friend, I'd say, 'Let's give it a try.' If you're a stranger, probably not, unless you had to make an emergency call," he said.

The call made from Schaffer's lawn went through but was quickly disconnected, apparently because of a weak signal. Schaffer did not seem to feel he owed any apology for the spotty coverage, though he did express concern for the person on the other end of the line.

"I know what it's like to have a call dropped," he said.

For all its limitations, the technology is starting to emerge commercially, with companies like Vonage, Skype and T-Mobile now selling or supporting mobile devices that use Wi-Fi networks.

In some cases, the voice service is free. A Belkin phone that works with the Skype calling service costs about $180; calls to Skype users on computers are free, as are outgoing calls to domestic phone numbers, at least through the end of the year. Incoming calls from phones cost extra. Vonage charges $90 for a phone and $15 a month for 500 minutes of talk time.

One big hurdle is that the Wi-Fi radio frequency spectrum is unlicensed and not maintained by any one company, so call quality can be unreliable. Moving a few yards can require finding a new network to connect to. In other words, when you place free or low-cost calls - especially on a stranger's network - you sometimes get what you pay for.

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