EnvKey

EnvKey is a very interesting and useful developer tool that provides you with a secure, end-to-end encrypted environment for storing configurations, API keys, and other types of credentials.

Straightforward installation, login, and configuration procedures

Subsequent to a typical installation procedure and upon first launching the utility, you are required to sign up a new account by entering your email and the security token (which you will receive after you have entered the email).
You'll also need to create an organization by entering the name and a master passphrase (used for encryption purposes). From this point onwards, you should be able to access everything this app has to offer without any sort of hassle.

Manage API keys in a secure and specialized environment

You're provided with a clear-cut, intuitive GUI that allows you to access all your apps and all the connected users from the left-side panel. For each app, there are a total number of four, self-explanatory sections: Variables, EnvKeys, Collaborators, and Settings.
In short, all your development, staging, production variables that comprise the development environments or sub-environments need to be added in the first section. As its name suggests, the second tab, EnvKeys, is the place where you can generate development or server EnvKeys with just a few mouse clicks.

Effortlessly add collaborators and grants various levels of access

The third section allows you to share your configurations securely. You can invite collaborators and grant three different access levels, ADMIN, DEVOPS, and DEVELOPER.
As you can imagine, the ADMIN level is the most powerful (view and manage all environments, as well as manage server access, edit app settings, and even invite collaborators) while the DEVOPS can only view and edit the environments, as well as manage the server access. Finally, there's the DEVELOPER level that only allows collaborators to view and edit the development and staging.

Improve the way you and your team manage API keys and configurations, as well as their security

EnvKey has a sense of security, innovation, and quality surround it. It's quite clear that a lot of work and thought has gone into making this app as secure as possible and also relevant for both individual developers or development teams out there.
It really does make managing environment variables and access tokens/security keys a whole lot easier. The only thing left to do now is for you and your team to give a shot.