Android 4.2 introduced a major change for tablets: multi-user profiles. This allows each member of the family (or organization), to have their own profile, complete with app, homescreen, and setting independence. Today, with Android 4.3, Google has taken multi-user accounts to the next level with restricted profiles. Essentially, this allows the tablet owner to have granular control over the other user accounts on the device.
For example, let's say you're a parent and you share a tablet with a young child. We all know how tap-happy kids can get, and many-a-parent has suffered the "my child just bought $86 worth of IAPs" tragedy. With Restricted Profiles, this is a thing of the past. The owner of the device – in this case, the parent – can set up a profile specifically for this child, and filter out all in-app purchases. This means that not only will IAPs unavailable to the little one, but they won't even show up in the first place. That's absolutely brilliant.
You can also control other aspects of the device: mature content filtering, access to games and user-generated content, and even specific applications. Developers will also be able to offer specific controls within their applications using the Restricted Profile API.
Restricted Profiles is available in Android 4.3, which is currently rolling out to the Nexus 4, 7, 10, and Galaxy Nexus (GSM), and comes stock on the new Nexus 7.