I understand that a blood glucometer or a halter monitor via a cellphone may sound cool, but the examples you provide represents niche products. Only a small fraction of the population would benefit from these abilities.
The problem arises when Apple takes these products to the masses. Any physician on here will tell you that these products are going to lead to a mess. If you take biometrics or blood tests or any test on the human body, there's going to be a not insignificant number of false positives. You apply this to over 100 million people and it's going to be a healthcare logistical nightmare. In order to do screening of a disease, it needs to be a fairly prevalent disease. If not, then doctors will spend their whole day working up mainly false positives.
And for a company that can't even produce a flawless fingerprint scanner, a technology that's been around for years, how are they going to fair with other biometrics? Measuring bodily functions and interpreting the results can be a very tricky business and I don't see a company whose major product is a cellphone doing anywhere near an adequate job.