Why do 100k people need a car battery monitoring app? The dial is right on the dashboard of the car, what does this app possibly do?! And drain your phone battery continously as well, is that really worth the ability to see on your phone screen what your dashboard already tells? And if it's for a stationary battery, why not just analog volt meter dial?
Sorry for complaining, but it's so hard to find standalone devices that don't require an app nowadays (simple example: try finding an LED lamp where you can choose the light color that allows doing it with a button on the lamp itself without app - I found one but it was non-trivial and it still doesn't allow color cycling without app). If people wouldn't prefer this BS, it would be easier to find sane electronics/electrics again.
The battery is there to start the (ICE) car. Its voltage under ~500 of amps of load is the relevant voltage. The voltage when the car is off is almost always irrelevant (it provides no guarantee about the ability to crank) and the voltage when the car is running is doubly irrelevant (alternator). What you want to do is watch and record the voltage dip while cranking, and this alone will give you a sense of your battery health.
If it's this important, does the onboard computer of the car not check this and warn if needed? If not, why not and why did humanity end up in a state where clunky apps are needed for this when the car already has all the electronics it needs for this?
People are accustomed to the coping mechanisms: aggressive battery replacement (on a schedule / at the first sign of struggle) or letting the battery deteriorate until the car fails to start and then asking for a jump / calling a tow truck. People see these inconveniences as inevitable, not as the result of a missing feature that really ought to be standard. Manufacturers don't feel pressured to do better so they don't do better.
If not, why not and why did humanity end up in a state where clunky apps are needed for this when the car already has all the electronics it needs for this?
(Almost) No one is making their car purchasing decisions based on the existence of a car battery health feature.
I mean, probably nobody looks at whether a stick to measure the oil level is integrated in the oil cap either, but it's still there fortunately (or do you need an app for that too these days?)
Unfortunately, a lot of vehicles these days, mostly high-end, do not come with oil dipsticks anymore[0]. I know that Audi starting switching to sensors-only around 2012, and I believe BMW started even earlier than that.
Sorry for complaining, but it's so hard to find standalone devices that don't require an app nowadays (simple example: try finding an LED lamp where you can choose the light color that allows doing it with a button on the lamp itself without app - I found one but it was non-trivial and it still doesn't allow color cycling without app). If people wouldn't prefer this BS, it would be easier to find sane electronics/electrics again.