[xp84]

> there's plenty of other reasons they can fail that you're already living on the edge if all you're carrying is your phone

I see what you're arguing, but I just want to point out 2 things:

1. If I leave the house for a trip (especially a distant trip) with just my phone, I and anyone would understand intuitively my own responsibilities: namely, to keep my phone intact and its battery from draining completely. Since I already have a strong interest in both of these for other reasons, this is basically automatic anyway, and a backup plan for the latter is completely doable - I'd have to drop $20 on a gas station phone charger and hang out somewhere for 10 minutes while it goes from 0->6% or whatever. Anyway, if I understand my responsibilities like this, I'm able to make an informed decision on whether to trust it.

2. If we're victim-blaming here, saying "Serves him right, should have carried the keyfob as a backup" that renders it pointless to even have phone-as-key. The fob not having to be in your pocket or handbag is the only benefit. Unless, I suppose, you consider phone-as-key as the actual backup, for use only in the case you drop your keyfob into a storm drain. But that isn't how it's marketed at all. In my entire life, I've literally never lost my car keys, because they just stay in my pocket the whole time I'm away from home. So I'd value a 'phone-as-backup' at $0.