FORTUNE — Has 24/7 access gone too far? A small but growing number of companies are encouraging their staff to take time off from their BlackBerrys and smartphones or reduce their dependence on email. No one disputes that these gadgets help staffers stay connected to coworkers and clients, but constant connection can lead to exhaustion and a decrease in productivity.

Seeing that his staff felt that they needed to be accessible 24/7 seven days a week back in 2007, Sam Chapman, CEO of Empower Public Relations, a 25-employee Chicago-based PR firm, cut the smartphone cord. He established a BlackBerry Blackout Policy, which prohibited the company’s staff from answering calls or emails from 6 p.m. to 6 a.m. weekdays and from Friday night to Monday morning. Empower went cold turkey on electronic gadgets after work except for the “once a year emergency,” he said.

Chapman says that his agency is thriving and attributes some of its success to having an energized staff, not an overburdened one. “When staff is at work, they’re focused. When they’re off, they take a break and recover,” he said.

When Chapman was out to dinner with his family, he could feel the BlackBerry vibrating in his jacket pocket, insisting to be answered. “Now I turn everything off. It’s good for my family and my psyche,” he said.

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Clients have adjusted to not being able to reach Empower’s staff after working hours. Most consider the break healthy and only try to reach staff if a legitimate emergency arises, said Chapman.

Moreover, the move has boosted retention. Empower PR has lost one person annually over the last few years. By comparison, several years ago, back when the firm had 10 or fewer employees, it was losing 50% of its staff every year. Chapman also says he now can recruit talented workers who seek a break from 24/7 availability.

Cutting out email

In February 2011, Thierry Breton, CEO of Atos, a French global IT services and consulting company with 70,000 employees in 42 countries, announced a three-year “zero email program.” Despite the lofty name, the project isn’t aiming to eliminate email, but drastically reduce its use. Email will only be used at Atos for vital customer communication and where it’s required for documentation or legal reasons, but staffers are otherwise expected to communicate the old-fashioned way, by telephone or in person.

Robert Shaw, global director of the company’s zero email program, said Atos believes that “email has become overused. People are losing productivity because they’re spending so much of their working time focusing on their inbox.” Atos analyzed email use at the company and determined that 90% of emails didn’t lead to a productive result and only 10% reached resolution.

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The company’s employees are being trained to use alternative methods such as group instant messaging and workflow, an internal process which allows for approval/rejection items such as travel authorization. They are also being encouraged to return to what Shaw calls “a cherished practice of talking to each other face to face.” Moreover, many of Atos’ clients are eager to hear the results of its three-year project. They think their staff is spending too much time on email too, Shaw notes.

The Blackberry time-suck

What started as a project to boost work-life balance at the Boston office of the Boston Consulting Group (BCG) by Leslie Perlow, a professor at Harvard Business School, turned into a way to redefine teamwork by reducing 24/7 BlackBerry access. Perlow concluded that most consultants created self-induced pressure to stay in touch with colleagues via BlackBerry. Clients weren’t demanding full-time access, and most non-work hour conversations were among teammates. Most consultants balked about relinquishing the use of their BlackBerry, even for one night.

In her book Sleeping with Your Smartphone, Perlow called this behavior “the cycle of responsiveness.” She started working with three teams at BCG in 2008 (which eventually turned into a study of 1,000 teams) to determine how they could change how they work together and reduce the 24/7 communication. To break this cycle, Perlow introduced small changes she called “predictable time off.” When one consultant took a BlackBerry break Wednesday night after 6 p.m. until the next morning, a colleague would cover in case of an emergency, freeing the consultant from worry. Moreover, the team met weekly to discuss how the plan was working.

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Of course, BCG consultants were still reachable by BlackBerry 24/7 the other six days a week, so this experiment didn’t radically diminish their on-call responsibilities. Perlow said, “It doesn’t make a tough job easier; it just makes it better.”

“Our staff didn’t mind working hard, but what they missed was the lack of predictability in their life,” explained Deborah Lovich, head of consulting and business services at BCG’s Boston office. Now they could make a dinner reservation and know they wouldn’t miss it because of work. In the past, BCG consultants didn’t work 24/7, but they were on call 24/7.

When the firm’s staff was forced to turn off their gadgets for one day, it encouraged them to prioritize their tasks, rethink how they were spending their time, and even work better as a team, Perlow says. The project has been so successful that 69% of all consultants in BCG North America now turn their BlackBerrys off one day a week.

Perlow surveyed two types of consultant groups: those who took a day off from Blackberry use and a control group of employees who didn’t and compared their attitudes on staying at the firm and work life balance. Fifty-eight percent of the BCG employees who separated from their BlackBerrys said they were likely to stay at the firm. By comparison, just 40% of those who had continued with their normal smartphone use said the same thing. And 54% of the BlackBerry blackout group reported a solid work life balance, compared to 38% in the control group.

When Perlow surveyed clients about BCG’s consultants taking a night off from availability, most hadn’t noticed any change, underscoring the theory that most consultants either impose the 24/7 approach on themselves or are responding to peer pressure.

Taking that one night off and keeping communication lines with your coworkers open “creates more openness and ability to discuss issues about work and personal life. It creates more passion,” Perlow said.