Spark vs Opal

The most interesting thing in Opal's documentation is their recommendation for people who need a genuinely hard block: have a friend or family member set the Apple Screen Time passcode so you do not know it. That is sound advice, and it concedes the structural point — software running on a phone you administer cannot hold a line against you without someone else holding a credential.

A physical key is the same idea with the social cost removed. Instead of asking another person to hold a secret and be available whenever you need it changed, you leave an object in another room. Nobody has to be involved, nothing has to be negotiated, and the credential cannot be talked out of you.

That is the whole comparison, with one thing it is not. On features, analytics and polish, Opal is ahead, and it would be silly to claim otherwise. On the specific question of whether the block survives a bad Tuesday without recruiting a friend, a key in the hallway is a different category of answer — and it is bought once rather than renewed every year. It is not a stronger lock at the operating-system level: on iPhone, Spark relies on the same Screen Time permission Opal does, which you can revoke in Settings, and deleting the app ends a session. What changes is the everyday route back in — not a trip to Settings, but a walk.