Pi-Star has had some basic integration with the BrandMeister API for some time, allowing information about your repeater to be read from the BrandMeister network, however all of this information was only available as read-only;
Until now that is...
Step 1 - Obtain your BrandMeister API Key;
Login to the BrandMeister dashboard at: https://brandmeister.network 
Step 2 - Click your callsign at the top right
Click the "Profile Settings" option.
On the new page, click the "API Keys"
Now on the API Keys page, click the "Add" button on the right hand side.
You will be prompted to give this key a name, for this example I call it "Pi-Star"
Now you will be presented with your API key, you will want to select all of the text in the text area at the top, and copy that (right click, copy) for use on the Pi-Star dashboard in the next step.
Once you have the text copied, press the OK button.
Navigate to your Pi-Star Dashboard, we need a page that is not currently available as a link (although it will be added soon): http://pi-star.local/admin/expert/edit_bmapikey.php 
Here we enter the API key we obtained in Step 2.
Paste the key into the box, and apply the changes;
Thats all there is to it, the next time you use the "Admin" link in Pi-Star, you will now have access to the API features that look like the below: