Is it a ChromeBook? An iPad? Perhaps a LeapPad? No, none of those. I doubt you've seen it before.
The simplest personal computer begins with a single button. The user gets one thing to do: press the button. That's also what it looks like, one button beckoning "press me". Most likely on a touchscreen.
This computer is unusual in that the simplicity isn't hiding anything; it's not a facade for apps, settings, or gestures to hide behind. Until the user presses the button, it's not possible for this computer to offer any value. There's simply nothing for it to do. Any value it offers depends entirely on the button-pressing pattern, now and in the future.
Each time the user presses the button, the computer saves the time. After two or three presses the next press can be roughly predicted by extending the time of the most recent press by the average of the last few intervals. This heuristic is rough but a fine place to start. Accuracy would be counter-productive anyway. When a prediction is available the user is visually informed of when the predicted press is expected.
So when is the button pressed? Like with regular computers, it's a garbage-in garbage-out situation. When just messing about it's all meaningless; the user won't see any value at all. If the user is earnestly pressing the button but for the wrong reason, they'll see very little value in it. However, there is one specific reason to press the button that opens up many interesting possibilities.
It's this: the user presses the button only when they take action in their life. Any action, no matter how major, minor, or how long it took, or whether it was just now, an hour ago, or yesterday. One press per action, no detail needed. For each button, the actions should probably be related. But it's all good as long as each button-press maps to a real action. While there's only one button at the beginning, there's no upper limit; the user decides what each button means, how many they want, and how they're organized.
That's the simplest personal computer.
Unlike how newbies first experience regular computers, you're already an expert on how to use it. I can say with great confidence that you're a button-pressing fiend and you're also the leading authority on what you get up to.
It's much more personal than usual because it's actually all about you. The only information to work with comes from your button presses about your actions; there's nothing else. Any structure that arises is of your own making, so you will understand it. And the overall simplicity means it works just fine without ever touching the Internet. That's wonderful for privacy.
From the time series, rough predictions are made about your future. This is because you are mapping presses to actions. The best predictions come from past actions, and that's exactly what the computer has to work with.
You might be surprised at how predictable you are when your various activities are isolated into their own frequency patterns. As modern ad networks demonstrate, there's tremendous value in behaviour prediction. Take it for your own benefit.
Build this simple personal computer yourself and see how far you can go. Or poke around for my take.