This app sends GPG-verified requests over the internet to a given server.
Currently there are the actions open and close, but request-type will be configurable. The request also includes a timestamp to verify the request is sent by the owner of the gpg-key and is not sent again by someone else.
It is used in the ChaosChemnitz hackerspace in Germany to open and close the door without the need of a "real" key.
Although APK downloads are available below to give you the choice, you should be aware that by installing that way you will not receive update notifications and it's a less secure way to download. We recommend that you install the F-Droid client and use that.Download F-Droid