Hi all, first post here - and never attempted anything Arduino before... so I need a baseball bat. Something that could plug into a usb port. I need to be able to measure swing speed, which I guess would be easy with an accelerometer. This is for a game, so it doesn't need to be accurate... also would really like to be able to know height above ground for more accuracy...
If anyone has any ideas, or anything... would really appreciate any help.
Would a hole be drilled into the bat and the arduino placed into the hole? I would think a sensor for detecting height would be very difficult. I'm not sure if an arduino would like getting swung like that (hitting a ball or no ball).
I think it would be a plastic bat - and no, no ball. It's to be the control for a batting game... and after a little thought I think height is not needed, all I need is swing start / speed which I think an accelerometer would be all I would need. For the most part, it would function like wii baseball - the pitch would be at a consistent height, so the only thing I need to care about is timing...
Try starting with this
and continue reading from there.
This seems to be better documented
https://www.sparkfun.com/tutorials/240
I remember reading that the incidence of smashed TV screens increased substantially after the Wii games were released, so you might want to make sure that your bat is tethered. 
Thanks, that accelerometer looks perfect. Now I just need to figure out how to get data from the Arduino to a JavaScript program.