SimonsVoss Key4Friends is a free Android app developed by SimonsVoss Technologies GmbH in the Utilities & Tools category. With this app, sharing keys with friends has never been easier and safer. The app works in conjunction with the MobileKey app, which the owner of the door uses to send an authorization for one or more doors to friends.

To get started, you only need to register with your email and phone number, and the app will send you a code by text message for verification. No password is required as the app uses the distinct connection between the SIM card and email address. Once you have registered, you can use the Key4Friends app to open and close the doors authorized to you.

It is important to note that your smartphone must be connected to the Internet to use the app. However, the amount of data sent is minimal, so you don't have to worry about incurring significant costs. Overall, SimonsVoss Key4Friends is a quick, easy, and safe way to share keys with friends, and we highly recommend it.