There are bike-friendly cities, and then there are places—like Amsterdam—with so many cycles on the street that people lock up at racks in multi-story garages, creating a completely nutso mass of wheels. How the hell are you supposed to find your ride at the end of the day? How about strapping on an innocuous-looking smart bell that tells your phone when you're getting close—and dings aloud to let you know.

Andrew Spitz and Ruben van der Vleuten—the brains behind design consultancy Frolic —made a fully-functional prototype in the lightning-quick span of a single day as part of their 24H Frolic series: ID a problem and fashion a solution without the time to overthink the particulars. And hey, whaddya know—this thing is pretty awesome.

They started with a regular bike bell then gutted the interior, adding back in custom electronics and 3D-printed parts. Part of the appeal is that it doesn't look like a device packed with any kind of special stuff, meaning someone might be less inclined to swipe it.

The gizmo connects to an iPhone via Bluetooth Low Energy (BLE); walking away after parking drops a pin where you're at, allowing GPS to guide you back. You can even remotely give the bell a ring-a-ling if you know it's right in front of you but just can't see it yet. I'm also picturing if your bicycle gets swiped, you could just repeatedly activate the bell and completely freak out of the thief. I'm excited to see what these dudes come up with in their free time next. [Frolic]