Smart lock vs lock monitor: which one do you actually need?
Search "smart home door security" and you get buried in options: smart locks, smart deadbolts, lock monitors, contact sensors. They are not the same thing, and most people only need one of them. Here is the plain-English difference, and how to pick the right one for your door.
A smart lock replaces your lock and lets you lock and unlock the door remotely. A lock monitor sits over the lock you already have and tells you whether it is locked or unlocked, without ever touching the mechanism.
If your real question is "did I lock the door?" rather than "I need to unlock it from my phone", a lock monitor solves it for a fraction of the price, keeps your existing keys, and cannot be hacked to open your door because it has no motor. If you genuinely need remote unlocking (holiday lets, tradespeople, keyless entry), a smart lock is the tool for that job.
This guide compares the two categories side by side so you can decide which approach fits your home, your budget and your security priorities. It also covers the newer option most comparison articles miss: a retrofit Matter lock monitor that reports lock state directly to Apple Home, Google Home, Alexa, SmartThings or Home Assistant, no lock replacement required.
One controls your door. One reports on it.
Before features and prices, it helps to be clear on what each product category is actually for. They look similar in an online listing but they solve different problems.
Smart lockReplaces and drives your lock
- Replaces your existing lock or cylinder
- Locks and unlocks the door remotely
- Usually needs a locksmith or careful DIY
- Motorised, so it is an attack surface
- Typical UK price: £128 to £425 plus fitting
Lock monitorFits over the lock you have
- Fits over your existing lock, cylinder untouched
- Reports locked or unlocked, status only
- Adhesive DIY install in about 5 minutes
- No motor, so it cannot be exploited to unlock
- Typical UK price: from £44.99
In one line: a smart lock controls your door, a lock monitor tells you about your door. The right choice depends entirely on which problem you are trying to solve.
Feature-by-feature comparison
The Locksure figures below are for the retrofit lock monitor. The smart lock column reflects mainstream UK Matter smart locks (Yale Linus, Nuki, Aqara U200, Bold and similar).
| Capability | Locksure lock monitor | Motorised smart lock |
|---|---|---|
| Check lock state remotely | Yes | Yes |
| Lock / unlock remotely | No by design | Yes |
| Keep your existing lock and keys | Yes | No, replacement |
| Install | 5 min, adhesive DIY | 15 to 30 min DIY, often a locksmith |
| Works on a UK multi-point uPVC door | Yes | No, often cannot drive multi-point |
| Renter-friendly, no cylinder change | Yes | Rarely |
| Can be exploited to unlock the door | No, no motor | Remote-unlock surface exists |
| Battery life | 18 months, CR2032 coin cell | Li-ion, recharge every ~6 months |
| Door open / close tracking | Yes, with optional £9.99 magnet | Extra sensor needed |
| UK price, device only | From £44.99 | £128 to £425 plus fitting |
Two categories, two jobs. The comparison is not about which is "better", it is about which question you want answered: "can I open my door from my phone?" or "is my door locked right now?"
If the thing nagging you is simply "did I lock it?", that is a monitoring problem, not a control problem. A lock monitor answers it on your phone from anywhere, keeps the lock and keys you already trust, and never adds a way for anyone to open your door remotely.
Never forget to lock your doors again.
Locksure fits over the lock you already have and shows its locked or unlocked state on your phone, from anywhere. No drilling, no lock replacement.
See how it works →When a smart lock makes sense
A smart lock is the right buy when you genuinely need to operate the door without being there. Common cases:
- Holiday lets and short-term rentals: issue and revoke guest access codes without handing over keys
- Letting tradespeople in: give the plumber a one-time code while you are at work, then remove it
- Keyless convenience: enter with a code, fingerprint or phone instead of carrying keys
- Auto-locking: the door re-locks itself a set time after it closes
If those describe your life, the higher cost, the fitting and the motorised mechanism are worth it. Just go in knowing a motor on your door is a mechanism that can, in principle, be commanded to open. That trade is fine for the convenience it buys, as long as it is a deliberate choice.
When a lock monitor makes more sense
A lock monitor solves the far more common problem: the need to know rather than control. It fits if:
- You just want peace of mind. The issue is wondering "did I lock up?", not needing to unlock remotely
- You are renting. You cannot swap the lock, but you can stick a monitor over it and take it with you when you move
- You value security. No remote unlock means no remote-unlock risk, full stop
- You trust your current lock. Maybe it is a British Standard cylinder you have no wish to replace
- You want to check on family. See that elderly parents or teenagers have locked up, without taking over their door
- Budget matters. A monitor costs a fraction of a smart lock system and there is no fitting fee
Plenty of people are uneasy about the idea that their front door could be opened over the internet at all. Even with good security habits, a remote-unlock capability introduces a risk that simply does not exist with a monitor-only device. For a lot of households, that alone settles it.
Two ways to add a lock monitor
If a monitor is what you want, there are two versions of the same proven Locksure hardware. Which one suits you depends on one thing: do you already run a smart home?
The Matter Lock Sensor
Already on Apple Home, Google Home, Alexa, SmartThings or Home Assistant? The Matter Lock Sensor joins your existing setup directly and shows lock state right beside your other devices. Ask Siri or Alexa "is the front door locked?", or trigger automations on lock state. It needs a Thread border router, which most smart homes already have (a HomePod mini, Apple TV 4K, Nest Hub 2, Echo 4th gen or eero 6+). No Locksure hub required. Add the optional £9.99 Open/Close Magnet if you also want door open and close tracking.
The Original Locksure
No Apple Home, Google Home or Thread router, and no wish to set one up? The Original Locksure is the same sensor hardware working standalone through the included Locksure display hub over your Wi-Fi. You get lock state on your phone through the Locksure app, with no ecosystem to learn, no Thread router and no subscription. Same 18-month CR2032 battery, same 5-minute adhesive fit. It has been shipping to UK homes since January 2025.
Either way the sensor is the same monitoring-only device: it reads the lock, reports the state, and never actuates anything.
The security trade-off, honestly
Smart locks are generally secure when set up well, but by design they add attack surface that a traditional lock does not have:
- Account compromise: if someone gets into your smart-home account, they may be able to unlock the door
- Radio and firmware bugs: connected locks have had exploitable Bluetooth and firmware weaknesses over the years
- Vendor dependency: you are trusting one company's security practices and update cadence for as long as you own it
A lock monitor has a fundamentally different profile. It cannot unlock your door because there is no mechanism to do so. The worst case if it were ever compromised is that someone learns whether your door is locked. Your physical security is exactly what it was with a plain lock. Locksure keeps Matter traffic encrypted at the session layer (AES-128-CCM) and holds no internet account on the device itself. For anyone who puts security ahead of convenience, that distinction is the whole argument.
Quick questions
Is a lock monitor the same as a smart lock?
No. A smart lock replaces your lock and can lock and unlock the door remotely. A lock monitor fits over your existing lock and only reports whether it is locked or unlocked. The monitor never moves the mechanism.
Can a lock monitor unlock my door remotely?
No, and that is deliberate. The Locksure monitor is monitoring only. It has no motor and no way to actuate the lock, so there is nothing on the network that could ever be commanded to open your door. The only way to unlock the door is still from inside, with a key.
Do I need a smart home to use a lock monitor?
No. If you already run Apple Home, Google Home, Alexa, SmartThings or Home Assistant, the Matter Lock Sensor joins it directly (you will need a Thread border router, which most smart homes already have). If you do not run any of those, the Original Locksure works standalone through its included display hub over Wi-Fi, with no Thread router and no subscription.
How long does the battery last?
About 18 months on a single CR2032 coin cell. The device reports its own battery level in the app on every event, so you get plenty of warning before a swap.
Will it work on my uPVC multi-point door?
Yes. Locksure reads the rotation of the thumb-turn or key, so it works on any UK euro-cylinder door regardless of the locking mechanism behind it. Motorised smart locks often cannot drive a multi-point system at all, which is one of the main reasons people choose a monitor instead.
Does the door open and close feature need anything extra?
Yes. Lock state works on its own. Door open and close detection uses the optional £9.99 Open/Close Magnet, so add that accessory if you want both.
Is a lock monitor allowed if I am renting?
In almost all cases, yes. It attaches with adhesive and leaves the cylinder untouched, so there is no lock replacement to clear with a landlord. It peels off cleanly and you can take it to your next home.
Just want to know it is locked? Start with the lock monitor
Locksure fits over the lock you already have and shows its state on your phone. No lock replacement, no drilling, no subscription, no remote-unlock risk, and the battery lasts 18 months. On a smart home already? Pair it over Matter. Not on one? The Original Locksure works standalone over Wi-Fi. From £44.99.