This is a combination of cool and scary. Researchers have found a signature in the brain that shows when a person is breaking a promise, and it shows up before the actual cheating occurs. They suggest that "breaking a promise triggers an emotional conflict in the promise breaker due to the suppression of an honest response," and this shows up in the pattern of activity in the brain.
While I certainly applaud the science, this is something that could easily be misused. I imagine people putting on electrode-studded helmets at job interviews, contract signings, criminal investigations or trials, marriage counseling, swearing in ceremonies, military induction, and any situation where a promise is made.
Is it fair to saddle such a wonderful discovery with the bad things people might do with it? Is it fair to blame physics for nuclear bombs? To blame the discovery of gunpowder for murders today? Only in a narrow sense.
So what should we do with the information? I'm afraid we don't have much choice. I predict that it will be used as I suggested above, and we need to either live with it or find a way to ameliorate the big brother aspects. I'm not sure what that way would be.