I don't think that Google's monopoly on the android setup is unwarranted. They both developed the OS software and host an app store where they decide what gets sold in this store - the same way that Apple does or Microsoft does on windows with its windows store.
> I should be able to install whatever app I want, without having to jailbreak my phone and deal with warranty nonsense from the manufacturer. Just like my computer, which I can also install whatever software I want on it.
I don't know too much about how the Apple/iPhone ecosystem works, but in both Android and in Windows you can generally download apps from locations other than the ones specifically sanctioned by Google/Microsoft without repercussions (android does have the setting you manually have to enable first before downloading external APK's). Google definitely does control an overwhelming share of the app download market, but that's because it has marketed itself well, it works well enough that users don't go looking for other stores, and there haven't been too many alternative stores that have sufficiently marketed themselves to general Android users (F-Droid is a cool concept, but the general Android user is more concerned with "getting an app that does x" than "getting an app that does x and the source code is available")