Like shown in the video the accelerator block can be used to speed other things up. But what's special about it is that it has physics which means that you can build inventions with it. You can place it wherever you want to (not like the conveyor-belt, which can only be placed on the floor).
The accelerator is the first block in a series of blocks that will allow you to create more dynamic things. Until now you could build different structures but everything in the game was more or less static. Furthermore, the next block that will find its way into the game will add a lot more possibilities what you can do with the accelerator and will allow you to build more complex machines which, of course, can also be used to defeat your enemy in multiplayer battles.
As the code restructuring is finished now (read the last post), I hope it won't be so long until the next update.
That's all for now, tell me what you think about this update :)