Think of it this way, chefs knives are legal. Murder is not. If you work in my restaurant, you can use the chefs knives to make food. You can't use them to kill people. If you do, you will be prosecuted.
Chef knife :: the app
Chef knife mfg :: the app developer
Murder :: stalking
Cooking :: legal tracking
The law prosecutes app developers and makes illegal apps that allow for stalking. :: The law prosecutes chef knife mfgs and makes illegal chef knifes that can be used for murder.
This is not you have stated. Your example world does not map to the real world, as it is a paradox to think a "murdering chef knife" can be discriminated from a "cooking chef knife" when the manufacturer creates it.
And that is the point of the parent commenter. A tracking app can be used for both legal tracking and stalking, but it is absurd to think the developer will know which it is.
You can certainly market your knives with an intention. You can study which knives "murder" best, and not study which knives are best for cooking.
I agree that this should be a harder bar to prove, but I don't think it's paradoxical to say it can be done.
> it is absurd to think the developer will know which it is.
True, the developer won't "know" for any given instance. But it is NOT absurd to think the developer will be trying for one or the other, perfecting it for that purpose (with intent), and marketing it for that purpose, nor is it absurd that such an intent could be reasonably proven. (Not ABSOLUTELY proven, but reasonably)
But there's also no law against selling knives designed for murdering people in many places. I mean I can walk into a store and walk out with a katana or a long sword or something. You're not supposed to use them for killing people, but that's literally the reason why they were invented. I don't want to say for sure, but I pretty sure the katana manufacturer is still not going to be liable if I go and hack someone up with my katana.
To the extent they are allowed – and this also goes for their more dangerous cousin, guns – it’s largely because there is a legitimate use case for attacking someone with a lethal weapon: self-defense. No such use case exists for a spying app.
[1] https://www.sword-buyers-guide.com/are-katana-illegal.html
There's not really a direct analogy there (an...invisible katana?), but I think the difference is clear.
If you want to directly monitor a child's or employee's usage, and/or restrict them from some sites/apps/settings, you probably want a parental/employer control app that doesn't compromise the phone to hide itself.
Have you read the article? These apps require you to disable important security measures on the target phone, leaving it vulnerable to attack, in order to hide the app from the user. There's no legitimate use case for that.
This is likely to lend render the manufacturer immune to any legal action.
If I sell a two-handed sword made with authentic 16th-century metalworking techniques, and I call it a "chef's knife" and talk about how great it is for cutting meat and vegetables and how it should never be used for historical European martial arts, then I'm being dishonest about something.
The manufacturer should make it obvious to the cook that their knife has been modified that way.
It is quite clear in this case that the app developer has developed the app to obfuscate this configuration, and thus shares in the responsibility.
In my example, the knife is the app.
In your example, the knife is the phone.
In my example, the sued knife manufacturer is the app developer.
In your example, the sued knife manufacturer would have to be the Mobile Phone creator. You intended for it to be the App Developer.
Regardless, much like the point of a knife is to stab, the point of a tracking app is to surreptitiously track. When a murderer uses a knife to stab a human, the murderer is at fault. When a stalker uses a tracking app to stalk, the stalker is at fault. Not the creator of the knife and not the creator of the tracking app.