That's right, besides knowing pretty much everything about you, if you let it, Google can now pull personal information directly from your body.
There are very palpable benefits to this; for example, your personal trainer, doctor or nutritionist will now be able to remotely monitor how your body works. Eat too many donuts, and your insulin level will skyrocket; but if you give access to your blood sugar level monitor to your doctor, he's going to have that "you're not listening to me" frown next time you visit him.
There are also downsides; I don't doubt that Google will take special care to protect the users' privacy, but still: are you sure you want to share your vital signs with...well, anyone online? The service is, of course, voluntary, but concerns are raised about the fact that this data can be used for health marketing; if Google knows you have a high blood pressure, it also knows which health-related ads to serve you.