Check them into your source control. If you can't build your iOS or OS X project without fetching source from somewhere that's not under your control, you're at risk of 😭 one day. It's fine to use dependencies but in my opinion, you should always be able to build your whole app purely from the content in your repositories.
That's fine if you're a solo developer if you're not then its a merge nightmare. No way.
Another situation when it would be fine is if you're developing a framework and include a demo/example project. Usually, if your framework itself has no external dependency there is no need for a complicated setup since cocoapods should be set up (here we are assuming you're using cocoapods since that's the topic of the article) to directly take the files from the /sources folder. If it has other dependencies though they will need to be already installed. You can't expect someone to be forced to run pod install when they only want to build and run the example application to see what's the framework's about or how it uses in practice.
In any other case, you're doing yourself a disservice by including the Pods. Only include in source control your application's code and resources. And this is not only true for cocoapods, but for everything. In JS you would never include node_modules. If you want to keep versions of the pods in syncs just pin them in the Podfile