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An unlock you have to walk for.
Spark's unlock is a proximity check, not cryptography: your apps open only after your phone has been held against your Spark — about 15 seconds for the Bluetooth key, a tap for the NFC one. It is built to beat an impulse, not a determined cheat. Here is exactly how it works, and exactly where it stops.
Four things this genuinely does
It takes the walk
The apps open only when your phone has been held against the key — about 15 seconds for the Bluetooth Spark, a tap for the NFC one. Across the room or on the next desk, it doesn't count.
Distance does nothing on its own
Nothing locks when the key leaves and nothing unlocks when it comes back. The app never shows you how far away the key is, because that is not what it checks.
No network in the loop
Your phone decides by itself, so unlocking works with mobile data off, on a plane, in a basement, and on a day our servers are down. Only pairing needs internet, once.
The key knows nothing about you
It carries an identity and nothing else — no secret, no app list, no schedule, no history. Losing it tells whoever finds it nothing about you or your phone.
What happens when you unlock
When you pair a Bluetooth Spark, the app asks you to hold the key against your phone and measures how strong its signal is at that distance. That reading stays on your phone. To unlock, the app listens for your key’s identity again, and accepts it only when the signal is about that strong — the key has to be against the phone — and only after it has heard it that way, without a break, for about 15 seconds. The NFC Spark is simpler: your phone reads the tag when you tap it.
Your phone makes that decision on its own. Nothing is sent to our server, so no network is involved. And nothing happens at any other distance: the key leaving the room locks nothing, the key coming back unlocks nothing, and the app never shows you how far away it is. Locking is separate again — a tap on Lock now, or a schedule — and never involves the key at all.
What the key holds
An identity, and nothing else. No secret, no app list, no schedule, no history — the key has no idea what it is unlocking, or that anything is locked at all. Pairing, which needs you signed in and online once, records that key against your account; each key belongs to one account.
Why that is not cryptography
Because the identity is fixed, anyone who records it has everything the key has. An earlier design had the key answer a fresh random challenge on every unlock, and an earlier version of this page described that design as if it were the product. Today’s key does not do it, and we would rather you read that here than work it out yourself.
What leaves your phone, and what doesn’t
- What you do on it stays on it. Your chats, your screens and what you do inside your apps never leave the phone.
- Your setup syncs once you’re signed in— and you sign in once, to pair your Spark. Your modes (with their app lists and websites), schedules, sessions, limits, the record of emergency unlocks you’ve used, and your settings sync to your account, so a new phone can restore them.
- Some things are sent even signed out. The app sends an install ID, fetches its settings, sends a short heartbeat while a session is running, and checks for updates.
- Buying a key is a separate record — an order with a delivery address. The privacy policy sets out what we keep and for how long.
What this does not protect against
None of these is hard for someone who has decided in advance to cheat. We would rather you read them here than discover them yourself.
- Recording and replaying the Bluetooth broadcast. The Bluetooth Spark sends the same identity every time. Someone who records it can play it back from another device held against your phone, and the phone will unlock.
- Copying the NFC tag. The NFC Spark is a standard NFC tag. It can be copied onto another tag, and the copy works like the original.
- Deleting the app on iPhone. iOS lets you delete Spark during a session, and deleting it ends the session.
- Turning off Accessibility, or Safe Mode, on Android. Strict mode makes Spark harder to uninstall or switch off while a session runs, and hides the emergency unlocks. It is friction, not a wall: switching off Spark's Accessibility permission or restarting in Safe Mode gets past it, and Settings itself can't be blocked.
- Anything that isn't this phone. A second handset in the drawer, the same site on a laptop, a factory reset. No app on your phone reaches any of those, ours included.
There are also five emergency unlocks, for a flat battery, a lost key or a real emergency. That is a deliberate way in rather than a flaw: five for the life of the app, they don’t refill, and Strict mode switches them off — an escape hatch that refilled would just be an unlock button with extra steps.
Not an attacker. The person this protects you from is you, forty minutes into a bad evening, reaching for the phone without having decided to. Against that, the key in the next room does not need to be uncopyable. It only needs to cost more than the impulse is willing to pay — and a walk and a fifteen-second hold are a cost your tired self cannot talk its way out of.
The five people actually ask
Can a Spark key be copied?
Yes. The Bluetooth Spark's signal can be recorded and replayed, and the NFC Spark is a standard tag that can be copied. It's built to beat an impulse, not a determined cheat.
Does unlocking need an internet connection?
No. Your phone checks the key itself — nothing goes to our server — so unlocking works with mobile data off, on a plane or in a basement. You need internet once, signed in, to pair the key.
Can I get around the block by turning Bluetooth off?
Turning Bluetooth off doesn't end the session — your apps stay locked. The blocking runs on your phone, not over Bluetooth; the key only matters at the moment you unlock, with your phone held against it.
What happens if the key's battery dies or I lose it?
Use an emergency unlock. There are five, for the life of the app; they don't refill, and Strict mode switches them off. The Bluetooth Spark takes a CR2032 coin cell from any shop, and the NFC Spark has no battery. If you lose the key, order a new one and pair it.
Can Spark see which apps I block?
Yes, once you're signed in — and you sign in to pair a Spark. Your modes (with their app lists and websites), schedules, limits and session history sync to your account so a new phone can restore them. What you do inside your apps never leaves the phone. Buying a key also creates an order with a delivery address, which the privacy policy covers.
The FAQ covers the rest — battery, uninstalling, whether it works on your phone. If your question is about what we store rather than what the key does, that is the privacy policy. If it is about the hardware itself, the buy page lists what is in the box.
A lock that asks something of you.
Locking is one tap in the app and works with Bluetooth off. Unlocking means walking to the key and holding your phone against it — which is why leaving it in another room turns a willpower problem into a walking problem.