Frothy profits are hard to come by for barrooms in this economy, so dozens of watering holes are hoping that a keg monitoring technology will help preserve profits—one perfectly poured pint at a time.

Close to 50 Massachusetts restaurants and bars have signed up with Syracuse, New York-based US Beverage Net Inc.’s flow meter system, which monitors every drop of draft beer by identifying how much has been poured and comparing that to how much has been sold. The system is designed to curb theft (usually in the form of bartenders giving away pints), identify faulty equipment or simply identify a bartender who pours beer incorrectly.

The flow meters have local restaurants buzzing about recapturing lost profits. Eateries are especially desperate to save cash in this market. Restaurant traffic dropped 2.6 percent during the second quarter of this year in the United States, the steepest decline since 1981, according to the research firm NPD Group Inc. in Chicago.

“I’ve always been interested in having a monitoring system,” said Dana Van Fleet, owner of the Cask ’n Flagon restaurant and bar in Boston. Van Fleet signed up for US Beverage Net’s system last October.

“As far as waste and theft, all you can do is keep it down because it’s going to happen no matter what system you have in place,” Van Fleet said.

Van Fleet said he wished he’d had the system last year when, after several months, he finally heard a bartender complain that one popular draft line was pouring too much foam.

“If you’re pouring a lot of foam, you’re pouring profits down the drain—we lost a lot of money” before it was fixed, Van Fleet said.

At the Cask ’n Flagon, about 50 percent of revenue (which the restaurant does not disclose), comes from draft and bottled beer. This year Van Fleet says he has seen a decline in business as Red Sox fans don’t arrive at Fenway Park as early for games, and they don’t stay as late. But he says those 81 sold-out home games make for a nice business boost.

US Beverage Net’s software-based system works by installing a 2-inch long “flow meter” in each beer line at the bar. The draft beer flow is recorded on the firm’s proprietary data box or “BevBOX” and that data is sent to the company’s Web site, where customers can log on to check their kegs.

The company uses a subscription business model and charges a onetime installation fee of $1,000 and $100 per month after that. That averages out to about $6 a day for the first year and about $3 a day—or one pint of beer—for subsequent years.