Imagine being able to check your medical history as easily as you can your e-mail. Or being able to provide records to a new doctor at a moment's notice. Google, Microsoft, and others are developing promising systems for storing digital health care records--for free.

But there's a catch (of course). Both the upcoming Google Health, currently in private testing, and Microsoft's public beta of HealthVault deal with our most personal information. The two projects will eventually enable doctors and hospitals to add records for hospitalization, doctor visits, and prescriptions (after you give your okay), and will permit you to upload data from devices that you might use at home, such as blood glucose monitors. They could be especially useful for allowing a new doctor to quickly confirm that, for instance, a prescription won't cause problems with other medications you're taking.

The drawback? The Health Insurance Portability and Accountability Act (HIPAA), a federal law that governs the confidentiality of health records, doesn't extend to non-health-care companies.