The short answer is that we plan to make all three, but we had to start somewhere, and we thought the "Socket" would be the best place to start. Why? Because it's a focused product with broad applications. That sounds like marketing mumbo jumbo, but let me explain.
Wall socket modules sound good in theory, but our experience with them is that, nine times out of ten, we use them for lights. So if that's the case, why not provide a better experience for lighting? By creating a light socket module, we can make something that works for both lamps and ceiling/wall lights, and provides dimming without risking someone dimming a television (note: don't try to dim a television).
How about a light switch? Well there are a lot of great things about a light switch - and perhaps the most important is that it can control multiple lights, which makes it cheaper if you want to use it everywhere. But the downside - and it's a big one - is that it has to be installed. This means messing with high voltage electricity, which can be dangerous and in fact in many states requires a licensed electrician, which makes the product expensive.
Now, it's not to say that wall outlet modules and light switches are bad products to make. They're on our road map, and the three products together will cover just about any lighting scenario you can dream up. But when it comes to the *first* product we'd make, we wanted the product that was most flexible, easiest to install, and easiest to use - and the winner was the Socket.