Coiled around a wind-swept hill near this city's lively Mission District, Bernal Heights takes an almost cult-like pride in being insular.

With a butcher, grocer, bookstore and bakery, the neighborhood provides the basics. When you add to that some unique establishments — like an organic baby food outlet and a knife-sharpening venture offering classes in Japanese whetstone techniques — many residents say they rarely feel the urge to leave.

"It's this weird little borderline utopia," said Ken Shelf, 42, who runs a combination movie-rental and succulent store here. His home, business, favorite shops and kids' school are all within a five-block radius.

Now, Bernal Heights is taking its experiment in localism one step further, adopting what is believed to be the country's first "complementary currency" in the form of a debit card.

Designed by two neighborhood loyalists versed in technology and banking, the Bernal Bucks card allows residents to pay for their purchases while earning credits every time they swipe it at any of the two dozen area businesses that have signed on since June.

Accrued as frequent-flier miles are, the bucks can be printed as coupons and used toward future purchases. Cardholders also can donate their accrued "wealth" to neighborhood nonprofits.

"The convenience of being able to use it anywhere and having your money increase in value because it's giving back to the community, those are really important things for Bernal residents to plug into," said Rachel Ebora, executive director of the Bernal Heights Neighborhood Center, which has started to pull in program-related donations.

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The idea of complementary currencies — which enhance but don't replace an official mode of exchange — is not new.

Massachusetts' Berkshire region has Berkshares, colorful bills bought with dollars at a slight discount. In California, Davis Dollars (adorned with a bicycle) have circulated for a few years. And two Marin County communities recently began minting $3 tokens at a discount that are handed out as change. They can be spent at participating merchants or pocketed as souvenirs.

Other currencies that encourage local trade or barter have sprung up in Sweden, Japan, Kenya, Venezuela and Britain, among other countries.

The downside of most of the programs, advocates concede, is that consumers have to carry two kinds of cash. And the most-engaged merchants often get saddled with registers full of funny money.

So Bernal residents Guillaume Lebleu and Arno Hesse worked out an electronic solution.

They met at an "unconference" on banking innovation in 2009. Both had been pondering how communities could bolster their economic health in the face of the national downturn. After hosting a forum to toss around ideas, they began distributing $5 bills to merchants marked with Bernal Bucks stickers.

Residents who reused the bills locally, in what Lebleu called "probably the neighborhoodiest neighborhood in San Francisco," got a token of appreciation: a crisp apple or an upgrade to a larger coffee.

The stickers raised awareness, Hesse said, but their potential was limited. Fortunately for Bernal, he and Lebleu had the background to take it to a higher level.

The soft-spoken Lebleu, 36, had developed financial software and long pondered the ways technology was "changing money itself and, with it, our communities and society."

The 50-year-old-Hess was a former Union Bank executive who had been involved in the Slow Money movement, which urges resident investment in the local food supply — with often unconventional returns. (His own investment in a Vacaville organic farm earns him a steady supply of eggs.)

Bernal Bucks is the pilot program of a company Hesse and Lebleu formed last year to promote community rewards networks.