Urban cyclists have more in common than an aptitude for pedaling through city streets — they share the ever-present dread of one day discovering their bicycle missing from the bike rack, or finding only the skeletal remains of its wheel-less frame.

These days, the standard U-Lock is no match for saw-wielding thieves, who are also quick to yank a bike from a locked rack on the back of a car or break through a garage door.

But if kryptonite won't stop bike thieves, a growing crop of entrepreneurs are hoping that new technology will outsmart them.

"Everybody who does urban cycling gets their bike stolen at some point," said Niko Klansek, founder of New York-based FlyKly, which makes Bluetooth-connected bike parts. "We have to live with this until we figure it out."

Start-ups from San Francisco to San Jose, Paris to London are building high-tech locks, alarms and tracking devices that aim to deter thieves and help cyclists recover their stolen wheels.

Wi-MM, a three-person start-up in Santa Clara, Calif., has built an alarm that's concealed inside a water bottle holder attached to the bike frame. The device will make a blaring siren-like sound if the bike is moved or tampered with after it has been locked. The owner receives a text message that reads: "Your bike is being stolen as you read this message."

The hope, co-founder and Chief Technical Officer Les Levitt said, is that the owner can stop the theft in action, if the alarm didn't scare the thief off.

"It's like the barking dog — the thief will move on to the next house," Levitt said.

FlyKly, which publicly launched at the recent Consumer Electronics Show in Las Vegas, makes wheels that include a motor and connect to a smartphone app. With a swipe of the app, the rider can control pedaling speed and braking, and also lock the rear wheel. And every bike is registered to a user through their smartphone, so if a stranger starts pedaling a bike, FlyKly is alerted.

Tracking devices could help recover stolen bicycles by marking their location on a map — no matter who is riding it, hauling it in the back of a truck or selling it at a flea market. The Wi-MM device includes GPS and works on the Verizon network, so as long as the bike is within range of a Verizon tower, its exact location can be tracked, showing up as a red dot on a map.

United Kingdom-based Integrated Trackers makes GPS trackers that mount to the bike's steering tube or can be disguised as a rear light. "You can watch the red line trace from where the bike was stolen all the way back to the thief's house," founder Harley Clark said.