A lot of ARM SoCs, particularly in the mobile world, have always had features like this. Apple even explicitly advertises it as a security feature on their iDevices. I think the difference here is because x86/PC has traditionally been one of the more open platforms, so attempts at locking it down are more strongly opposed. The PC is one of the few remaining computing devices where you can still inspect, modify, and develop with relative freedom.
There's a lot of new stuff coming in the ARM world which goes way beyond what they have today. (I know about a couple under NDA, and about the current state of the art, so I have to assume there are others).
The best "demo" of this in a fairly open way is USB Armory; they exposed the best features currently available in a developer friendly way. But there are some other things coming which are even better.
(I care about end users being able to trust remote servers; I don't really care about remote content owners being able to trust local client devices. There are usually no rights issues with the former, and DRM is the obvious (but not only) use case for the latter. I generally believe whoever buys a piece of hardware deserves full rights to it, but there are cases where that's an organization and they have ever right to expect all of their widely-deployed hardware is untampered...for instance, a closed computing environment for processing PII of third parties.)