© Stiftung Jugend forscht

Katharina Häußler (17) and Annalena Pleß (17) from Stuttgart have developed a clever smartphone app that helps people find lost items. The principle: the bunch of keys is fitted with a small chip that communicates with the smartphone via Bluetooth. If the keys cannot be found, a search query via the app is all it takes - and the bunch makes itself known with a buzzing sound. The highlight: 'Custos Clavium' - 'Keeper of the Keys' - also works over long distances, i.e. outside Bluetooth range. This is because the app can remember the last registered chip location and report it to the desperate owner if necessary.