The Stemlock is a permanent bike add-on that renders the handlebar useless until unlocked. That means, whoever is riding can't steer the bike properly, potentially resulting in a few minutes of entertaining bike accident videos. Get your cameras ready.
Despite the potential for pranks (and the occassional injury), the Stemlock is actually intended as an extra layer of security for bikes. While a thief can obviously still pick it up and run with your bike after he manages to get past your Folding Bike Lock, the difficulty of that whole ordeal (pushing a bicycle on foot for a few blocks doesn't sound all that fun) just might be enough of a deterrent to make them give up.
To use, you will have to install the Stemlock, integrating it with both the handlebar stem and the fork. The rig comes with a keyhole on the side which, when unlocked, allows the bicycle to function normally. Once locked, however, it disengages the stem from the fork stay, so you can swing the handlebars left and right with zero effect on how the front wheel turns. An additional benefit: this gives the bike the ability to minimize its width (turn the handlebars parallel to the frame), allowing you to park it in narrower-than-usual spaces. Oh yeah, the rig uses multi-combination screws that require a bundled tool to remove, making it just a little more challenging for thieves to dismantle (unless they also have a Stemlock, at which point, you lose).
While creator IXOW is marketing the Stemlock as a standalone anti-theft device, we doubt people will ever be at ease relying on this alone as protection. It is a nice additional annoyance for thieves, though, which adds a couple of extra benefits as well. Release is slated for August, priced at €74.90.