None of what your describing sounds good... at all. At least to me it doesn't. We don't constantly know our body temp because we don't need to constantly know our body temp. The symptoms of a cold are your clue you're getting a cold. Multiple ailments exhibit similar conditions in the body. Abnormal temp could be a sign of a cold, the flu, or your house is on fire and you should probably find an exit.
The point is you don't know what the data will show until you've collected it. We can guess all day long, but a lot of very useful medical discoveries (of which I am sure you are benefiting from today) were born out of a very large and detailed data set being collected. Beyond medical, it can also help urban planners design cities, or architects design buildings, or financial institutions to customize insurance, etc.
I used the cold example because it's one most folks can relate to, and its also immediately practical. With good data, the computer can notice patterns, such as that you wake up with a temp of between 96.7 and 96.9 every day, warm up to between 99.6 and 99.8 during a morning workout, cool down to between 98.2 and 98.4 by lunch, and end the day at between 98.9 and 99.1. None of this has be tracked by you, or even checked by you, it can be done in the background entirely; meaning you don't have to "know" it or be thinking about it at all.
It can notice an anomaly: say you wake up with a temperature of 97.4, flag raised. By lunch you're at 99.1. It's not something we would normally even know today, but it's a sign that you have a fever coming on (certainly not a house fire, else the smart smoke alarm would have noticed). Maybe it sends your phone a notification explaining that you might have a fever coming on, suggesting you eat a healthy meal, drink some herbal tea, and maybe plan for a few extra hours of sleep that night. By the time the symptoms of a cold are strong enough for you to notice on your own, it's too late. By that time, you're already past the cold and your body is fighting it off. But if you can know when one is coming on before the symptoms hit, you can at least attempt to nip it in the bud before it forces you to miss work.
It doesn't even have to be right or useful every time, as long as it's right or useful some of the time is fine. I remember some economists calculated that some very large number of US productivity in dollars is lost due to mundane cold and flu symptoms every year (I don't pretend to remember the number, but it was large, surprisingly very large). If this kind of automatic flag-raising and data-driven lifestyle advice can reduce loss of productivity by merely 5% (meaning 95% of the time it doesn't help the person defeat a cold early enough to not miss work), it would still increase US productivity by a huge amount.
All the while, the treasure trove of data could help researchers find links and causal connections between all sorts of diseases and symptoms that weren't evident before. Wouldn't it be useful if researched found a link between some easily-measurable vital sign and a disease that normally has a very long incubation period?
Ebola, for example, can have a very long incubation period (over a month sometimes), so it's very difficult to know when someone has it before they show noticeable symptoms, at which point it might be too late. However it would be very useful to get them treatment before the symptoms hit. Wouldn't it be wonderful if the data revealed some clues in a persons vital signs that are too small to be detected by a casual observer but which, as a pattern, always manifest weeks before Ebola is fully incubated in a human? Unfortunately because Ebola is pretty rare, links like these are impossible to find unless we have enormous mountains of data tracking tens if not hundreds of thousands of people for many years.