I’ve seen lots of so-called “smart” bike locks over the years, but none so far could justify the added cost. A newcomer that got its start securing ATMs for banks is trying to change that. There’s nothing wholly unique about the TMD Chain Lock, but the combination of materials, performance, and insurance-friendly ART-2 certification makes it worth considering.

TMD’s first bicycle lock combines a Bluetooth proximity sensor and motion alarm with a slender core of hardened steel chain wrapped in a soft and lightweight sleeve of high performance Dyneema and Kevlar fibers. That makes this lock tough, yet flexible enough to conveniently wrap around your seat post when cycling. TMD also designed the keyless lock to be shareable with friends and family, and capable of withstanding shock, rain, dust, and extreme temperatures. That makes it highly suited to city bikes parked outside and ridden all year long.

I like the TMD Chain Lock I’ve been testing, but spending €249 (about $283) on something that typically costs far less is a big ask.

The chasm separating ATM security from bike security isn’t as wide as it might seem. TMD developed a centralized, keyless system for banks to authorize access to its ATMs for service, replacing the physical master keys that created a massive security risk whenever they were lost or stolen. It’s this same keyless knowhow that TMD now brings to the Bluetooth bike lock.

There are many advantages to turning phones into digital keys, especially in bike-centric societies like the Netherlands, which TMD calls home. For example, I could ride to the train station and have an authorized friend pick the bike up later. And the keyless convenience quickly adds up for those of us that use our bikes to commute to work, pick up the kids from daycare and football, run errands, and shop for groceries. In my home city of Amsterdam, it’s not unusual to grab my keys more than a dozen times a day to lock and unlock my bike.

I tested the TMD Bike Lock in the 110cm (about 3.5 feet) length with an iPhone 15 Pro running the latest version of iOS. Generally — I’d say 19 out of every 20 attempts — the TMD Chain Lock immediately recognized my approach, allowing me to seamlessly unlock it with a push on the lock’s only button. When I did have to wait, it took no more than a second for the button to flash blue, indicating the lock had detected my nearby phone in a pocket or bag. Pretty good, but that convenience comes with some tradeoffs.

For example, my bike remained within range of my phone when parked outside a cafe, so anyone could have walked up and unlocked it. I had the same issue when cooking in my kitchen with the bike parked just outside the window, as I normally do. In both cases, I either had to move the bike or turn off my phone’s Bluetooth radio. And since my phone is now my bike key, if it’s stolen, my much more expensive e-bike is vulnerable as well.

TMD says its Chain Lock is “immune to conventional drilling and picking,” but all bike locks can be defeated by a determined thief. The Chain Lock has earned an ART-2 certification issued by an independent Dutch organization that tests and certifies bike locks on a scale from one to five. Most Dutch insurance companies require ART-2 at a minimum to validate policies on expensive e-bikes and cargo bikes. It’s akin to something like a Sold Secure Silver or Gold rating in the UK, a 2 Roues in France, and VdS approval in Germany. (The US and Canada do not have a single, centralized, independent testing body that dictates insurance requirements for bicycles.) Should your bike be stolen, you can produce a digital log file for the insurance company from within the TMD app as official proof that your bike was locked.

To deter theft, the lock also features an integrated motion alarm that can be armed and disarmed in the app or with a double press of the lock’s button. At 100dB it’s less shrill than I expected, but it does the job when it senses the lock being jostled. It shuts off automatically after about 10 seconds of inactivity.

The lock is rather noisy in day-to-day usage. Unlocking it is accompanied by a loud tone that hits 75dB when measured at a distance of one meter. I hate that it draws attention to me and my expensive e-bike. Just flash green and unlock — that’s more than enough. TMD tells me that a future software update will let you disable these sounds.

TMD claims the lock’s battery will last up to nine months on a single charge. However, my test unit has already dropped 16 percent after a week of testing, suggesting a lifespan closer to six or seven weeks. But that’s likely because I store my bikes inside my house when not in use, so the lock’s Bluetooth radio is constantly being lit up by my phone’s proximity.

To prevent water and dust ingress and leave more room for the battery and speaker, TMD says it opted for a shallow magnetic pin connector – not USB-C – to charge the Chain Lock. That’s a shame because plenty of phones have USB-C ports and offer even better IP68/69 protection against rain and debris. That means you’ll need to have the lock’s proprietary cable on you should you ignore the low-battery warnings and let it die. It can be quickly recovered, however: I saw a completely dead (and locked) Chain Lock spring back to life after just two or three minutes of charging off the USB-C port of an iPhone.

You can still unlock the TMD Chain Lock should your phone die. You just have to tap in your four digit “emergency code” on the lock’s button. Choosing a code like 1324 would require 1 push, then 3 pushes, then 2, and 4. The ring around the button changes colors to visually prompt you for each new number. The TMD app also lets you share the lock with friends and family, who can also come to your rescue with their own phones.

For added peace of mind, it’s always a good idea to double-lock your bike, so most urban cyclists combine a chain lock with a ring lock that’s permanently mounted to the frame and prevents the rear wheel from spinning. TMD has already announced an “anti angle grinder” U-Lock and GPS-equipped Ring Lock coming later this year. Having my phone unlock both of my bike’s locks simultaneously would really up the convenience factor and better justify TMD’s pricing.

Right now, paying €249 when equivalent analog bike locks costs a quarter of that would be foolish for most people. The ART-2 certified ABUS 8900, for example, in the same flexible 110cm length, costs around €60 (about $68). If you can afford the TMD Chain Lock and really hate keys, or need a keyless lock that can be shared digitally with others, then have at it. Otherwise, it won’t justify its exorbitant price.

All photography by Thomas Ricker / The Verge