Can a tag work in a car several people drive?
Only if the tag carries an address that any phone can follow. A routine configured inside one driver's automation application exists on that phone alone, so every other driver taps the same tag and gets nothing at all. The tag looks identical in both cases, which is what makes it confusing.
Where the behaviour lives
If the tap is handled by an automation on your phone, the tag is personal. Another driver taps it and the phone does nothing, because nothing on their phone knows the rule.
If the tag holds an address, any phone that reads it follows the address, with no configuration on anybody's part.
The tag is byte for byte identical from the outside in both cases, which is why a household concludes the tag is broken when it is merely somebody else's.
Building for several drivers
Write an address and nothing else. Resist the pull towards a routine, because a routine is more capable and only works for one person.
Test with a phone other than the one that wrote the tag, ideally on the other platform. That single test catches almost every version of this mistake.
And leave the tag unlocked, since a shared car outlives the reason the tag was written.
What is worth putting there
A navigation destination that everybody uses, such as the depot or the site.
A page holding what any driver might need: the insurance reference, who to call, where the service book is, which fuel the car takes.
A form for logging a journey, if journeys have to be logged, since a form opened by tap is far more likely to be filled than one somebody has to find.
Keep personal details off it. A tag in a shared cabin is readable by anybody who sits in the car, and there is no way to restrict that.
The handover case
Cars that pass between people have a recurring problem: the state of the car at the moment of the handover, and nobody writing it down.
A tag on the console that opens a short form turns that into a five second habit, which is roughly the amount of effort a handover ritual can survive.
What it cannot do is verify anything. The tap records that somebody opened a form, and the honesty of the entry is the same problem it always was.
Frequently asked questions
Why does the tag work for me and nobody else?
Because the behaviour is on your phone rather than on the tag. Replace the routine with an address and it works for everybody.
Can each driver get their own routine from one tag?
Yes, if each configures their own phone to recognise it. That is several builds to maintain rather than one.
Is it safe to leave a tag in a shared car?
The tag is readable by anyone in the cabin, so treat it as public. Keep personal details off it.
Should the tag be locked?
No. A shared car outlasts the reason the tag was written, and locking removes the ability to correct it.