Giving away personal data in exchange for services can be a heavy trade-off.

On one hand, it seems obvious – just be careful about who you give your data to and what you post online, and give away as little as possible. But on the other hand, getting the benefits of apps that know enough about you to give you relevant information is really handy. For example, it might help to give Google Maps or Yelp your location when you search for a restaurant or want to know what the latest traffic updates might be.

So for privacy advocates, it’s good news that researchers at the MIT Media Lab seem to have cracked the code on this one. They have built a system for personal data called “openPDS,” which stores personal data and keeps it secure – but it also allows applications to access what they need to help you out.

The system is called SafeAnswers, and it allows users to take control of their data and process it either in the cloud or offline on a hard drive. Then, when apps ask for certain pieces of information, they can choose which questions to answer. For example, instead of giving an app exact location data, the app might ask instead, “Is this user at home right now?”

SafeAnswers could answer back with a simple yes or no using code, but it doesn’t need to give the app any more unnecessary information. The system focuses on metadata, which is the data stored on devices but is kept in the background, like time and location something was saved. This could make SafeAnswers a disruptive force in how we currently interact with apps, but that depends on whether the system becomes widely used enough.

Still, it could be handy for the more entrepreneurial consumers out there, who may be interested in selling their personal data to advertisers rather than giving it away for free.