What's the equivalent of "development pods" under Carthage?

I believe Carthage doesn't have something similar to "development pods" yet.

But you could simulate "development pods" just following these steps:

Steps:

1. Add the .xcodeproj to your workspace
2. Remove all the dependencies you have in your project of the framework you added in step 1. (probably you may need to remove it from Build Phases -> Run Script -> Input Files too )
3. Go to General tab of the target you want to run, add the framework under Linked Frameworks and Libraries (it is going to take the one added from the .xcoproj)
4. (optional) you may need to run carthage bootstrap in the framework's repo you want to add locally.

That's it.

After that you will be able to run your project and update framework's code in the same workspace.