There are a lot of alternative engine designs and technologies out there, more than a person can keep up with. This one, the Revetec, was pointed out to me (Thanks, Aaron), and comes from Australia. It's a boxer design but uses a central cam setup to harness the power from the piston. They have been working on this since 2001 and now have running prototypes and they've been looking for manufacturing opportunities with various companies. There has evidently been interest from Proton.
The design looks interesting. The size of the engine looks a bit large for motorcycles though it could be built smaller I suppose, they have a prototype installed in a large trike. The engine itself can be built with multiple cylinder configurations and displacements so it could be adapted to a wide variety of vehicles or stationary applications.
This is a lot farther along than the round engine I mentioned earlier. The question for anyone building a new design today is whether it will gain enough over current technology to make it a desirable alternative. This engine uses either gasoline or compressed natural gas which is a point in its favor, a diesel alternative might be a good thing, too, though there is no mention of that. This might be worth watching.