Fill in any domain name you control or use 'localhost' as your domain name. The domain linked to each key is used when authenticating the server-side flow. In your case you will not the using the server-side authentication flow so it doesn't matter.
What you're proposing is absolutely doable. We have something similar running internally at Podio to close issues in our issue tracker.
You will want to start by looking at the authentication options (I think app authentication makes most sense for you): https://developers.podio.com/authentication