This is some Black Mirror level garbage. If this becomes common place there'll be an explosion of automation devices to "use" your toothbrush a couple of times per day.
1. A rural area has few healthy eating options.
2. Everyone who cares about this sort of thing and has the means to move away leaves.
3. Healthy stores close because there are not enough customers.
4. Only junk food options remain. Now you've essentially increased societal segregation...
This may sound ridiculous, but it is already seriously hard to eat healthy in many areas of the country.
What do you think you need to eat healthy? Some meat, some fat, maybe a few carbs.
The burger patties at McDonald's are real actual 100% beef.
It's not particularly good food, especially if it is served slower than in their test kitchen, but come on.
Trans fats are more or less banned in the United States
Even butter has some naturally occurring transfat.
The granola bars I eat switched to unprocessed vegetable oil and upgraded their packaging (better oxygen barrier). A lot of products did that.
Why would they use an artificial sweetener when part of the reason the sugar is there is to help keep the bread moist?
I do agree that fast food isn't especially healthy, but the biggest issue is that people select meals that are much too large (especially if they get a sugar drink). The menus usually do have options that provide a reasonable number of calories (and cost less), so it is a choice.
[1]https://en.wikipedia.org/wiki/Sucralose
Edit: I don't know whether or not McDonald's in particular is using sucralose. I'm suggesting that it's a general trend, probably helped by the general public's distaste for things like aspartame, calories, HFCS, and so on.
The deep fried stuff I would avoid. The french fries, fish, chicken, it's all cooked in vegetable oil. Years ago they used beef lard, until they were pressured into switching. Now we know that cooking in vegetable oil is pretty much worse in every way but they haven't changed back.
Most people who look down on McDonalds would have no problem ordering a beer with their burger at a bar.
One could write software which runs on the toothbrush and reports back everything it can sense in the area. This grants the upstream provider up-to-date information on the environment where the toothbrush is. It's not hard to see how this is profitable in an age where spying is big business. This need not have anything to do with dentistry. Businesses are typically more interested in making more money than they are in adhering to someone else's vision of consistency.
How this data is used is, as always, up to those who possess a copy of the data, and utterly indefinable now. For all we know, it might be handy to know that a Bluetooth device with ID XYZ was present near a given set of global coordinates at a certain time of day and date. Asking how the data is useful is hard to say specifically like asking why a library (public or private) would have a copy of a particular work -- that copy might be useful to someone someday and it is easier than ever to get the public to cooperate in their own loss of privacy by framing every issue around convenience.