I'm currently working with Health 2.0 to access these technologies. In my opinion the most exciting of these is the challenge issued by Practice Fusion. This is the first time I have seen a vendor begin to open up their system.

As was stated in a previous comment, there are a large variety of applications which would benefit from access to actual medical data, and not require manuel entry. IMHO, this manual entry is why services like Google Health and Microsoft HealthVault will never take off.