Cycling Accessories

This Bicycle Alarm Calls Your Phone if Someone Tries to Steal It

Picture of bike thief with lock cutters escaping on stolen bike.

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There is no worse feeling than that twist in your gut when you get back to where you locked your bike for the day to find an empty space and a mangled D-lock. Your bike has been stolen, and you have no idea when, by whom, or where it’s been taken, and you have to begin to confront the fact that you’re unlikely to ever see that bike again.

But what if there was a way to be kept updated on the safety of your bike even when you aren’t with it? 

Luckily, there are bike security devices on the market that can be connected to your phone to give you GPS updates, push notifications and even alert calls that keep you in the know about the safety and whereabouts of your bike, no matter where you are.

Bike Alarm That Alerts Your Phone

If you need that extra bit of peace of mind when leaving your bike, investing in a bike alarm that alerts your phone is a brilliant idea.

There are a few of these alarms on the market: some alert you via an app and push notifications, and some even call your phone to let you know if your bike’s been moved.

One such example is AlterLock, an alarm/GPS tracking security system for bikes. If the device detects motion from your bike while it’s set in ‘lock’ mode, it will blare out a loud (95db) alarm, and then track the bike once per minute via GPS. If motion is detected, the Alterlock app will notify your phone with its own notification sound.

Leopard Lync is another smart alarm system which sounds a 109dB theft alarm, gives you instant theft alerts via the Lync app if unauthorised movement is detected, and has GPS tracking so you can keep an eye on your bike’s location. It uses 4G connectivity with global coverage.

There’s also the I LOCK IT GPS, which has real-time location tracking, a 110dB alarm triggered by intelligent motion sensors, an app which notifies you of any movement, and it can even be used to automatically secure your bike during short stops, such as at traffic lights, via the app or hand-held transmitter.

AlterLock: Bicycle Alarm with Phone Notifications

Let’s take a closer look at the AlterLock, which sends you phone notifications when movement is detected while your bike is locked.


Region Upfront Monthly
UK ✅ £95.99 £3.49
Europe ✅ €111.99 €3.99
Canada ❌ N/A N/A
Australia ❌ N/A N/A

Estimated pricing.

App includes ability to register a photo of your bike together with its specs and serial number.

Attached using anti-theft bolts only sold with this product.

AlterLock uses both GPS and Wi-Fi to determine its location accurately.

If AlterLock detects your bike is being moved, it sounds an alarm, deterring theft and interference.

  • Size: 15.9 mm × 3.8 mm × 0.9 cm
  • Weight: 50g

The AlterLock tracking device works through an app on your smartphone which sends location through GPS and Wifi. Alerts are pop up on your phone when your bicycle is moved and an alarm also sounds to deter thief’s, much like a house alarm.

In the event of the alarm sounding, the app also allows you to deactivate the alarm. Other settings can also be managed such as how long the alarm sounds for and movement detection sensitivity within the app.

In addition to this, the AlterLock app also has a function to upload a photo of your bike as well as specification information, such as your bikes serial number, to help retrieve in the event of a theft.

The tracking unit for the AlterLock fits underneath the bottle cages on your bike and is secured using specialist anti-theft bolts.


  • Aerodynamic
  • Includes alarm
  • Up to 1.5 months battery life


  • Expensive to buy
  • No USB cable included
  • Not well hidden

How Does AlterLock Work?

AlterLock fits onto your bike and notifies your phone when the device detects movement while your bike is locked away. It also blares out a 95db alarm – louder than a lawnmower – if your bike is moved while locked.

When motion is detected, the AlterLock app will call your phone with its own notification sound, so you can easily distinguish it from a regular text or phone call and instantly know that something is happening to your bike.

The ‘lock’ mode is toggled by you through the app, and you can also use the app to configure the alarm and set the motion detection sensitivity. Plus, as long as your smartphone is in close proximity, you can turn ‘lock’ mode on and off using a button on the device itself, which sits on or underneath your bike’s bottle cage, so you don’t need to take off your gloves and pull out your phone to get riding.

If your bike is unfortunately stolen – despite the loud alarm and alert – the AlterLock will track it once per minute with GPS so you can monitor its location. If it’s moved to a place where there is no GPS signal, the device then uses WiFi signals to determine its approximate location to help the police search for it.

AlterLock works slightly differently to other tracking devices in that it can track your bike’s location independently of your smartphone’s Bluetooth connection – so even if your bike ends up hundreds of miles away, the device will still transmit location information.

Where Is AlterLock Available?

The best place to buy AlterLock is directly from the AlterLock website, where it costs between £114.99 and £118.99 at the time of writing, depending on whether you choose standard bolts or anti-theft bolts. It’s also available on Amazon and at other retailers.

AlterLock Alternatives

There are a few products on the market that are similar to AlterLock, including the I LOCK IT GPS and Leopard Lync mentioned earlier. These vary in price and functionality, so it’s always worth shopping around for the device that best suits your needs and budget.

Many of these products cost upwards of £100, which might seem like a lot of money to spend. However, we’d urge you to consider the cost of having your bike stolen – it’s likely to be much higher than £100 – and the price of the heartache and stress associated with bike theft and security.

Some bikes even come with this technology built in – for example Urtopia e-bikes. As well as having a movement alarm that alerts you to unauthorised movement, these bikes have a GPS tracker connected to an app, a gyroscope to detect theft, and a fingerprint unlock system.

Is There a Bicycle Alarm That Calls Your Phone?

Yes! There are a few bicycle alarms on the market that call your phone as well as blasting out a  loud alarm when movement is detected. The AlterLock is a great example as it’s neat, unobtrusive and not too expensive, but products like the Leopard Lync and I LOCK IT GPS are similar alternatives.

These types of alarms can detect unauthorised movement and let you know via push notification that your bike is being moved while locked, so you can respond in real time by calling the police.

Many also offer GPS tracking functionalities, so if your bike is sadly stolen, you can track its whereabouts and improve your chances of getting it back.

Installing one of these alarms is a great way to give you some added peace of mind when leaving your bike unattended. It’s an unfortunate truth that bike theft is incredibly common, particularly in urban areas, and having a bike alarm that calls your phone will help you to respond quickly should the worst happen.

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