3密チェッカー is a free Android app developed by ラビットプログラム. It falls under the Lifestyle category with a specific focus on Health & Fitness. The app allows users to record and track their activities for up to three weeks. The recorded data can be viewed in detail through graphs, maps, and lists.

Before using the app, users are required to agree to the privacy policy. The app utilizes Bluetooth to measure the number of surrounding devices and tracks location information to record the measurement location. However, it is important to note that the developer does not collect any of the recorded data. All data is stored locally on the user's device.

It is worth mentioning that the app has received direct approval from the mayor of Ichinomiya City in Aichi Prefecture, Japan. Please note that the app is only available for use within Japan.