Windows: Security requires mutual trust. To that end, Secret Sharp allows you to share text-based information with a group of people that can only be decrypted if everyone (or a certain number of the group) collectively agree to access the secret.
While the sexiest uses for an app like this are probably not commonplace (most of you probably don't have a shared pool of mafia money stored in a secret Swiss bank account), it can be used for more common tasks. For example, sharing the combination to a safe or password to an online account in the event you're injured.
The app is simple enough and allows you to customise both how many people get a "share" of the secret as well as how many are required to unlock it. While you will need Secret Sharp to open it again, all of the shares can be entered in one place so only a single person ever needs to have the app installed.