Is there anything called vibration censor?

I was working a music system that changes the tempo of the music it is playing based on how hard you punch a boxing bag.

So basically, inside a room with a punchbag, I am going to place a comp and a speaker. The computer needs to receive data from some kind of censor that is attached to the punchbag. I was wondering what kind of censors I can use. As in the options available. My friend said there is something called vibration censor.

? ?

one of those? http://www.digikey.com/product-search/en/sensors-transducers/vibration/1966393?k=vibration%20sensor

If you need to measure how hard it is punched, you could use an accelerator sensor.

Google for : arduino punch acceleration sensor Like this one: http://www.youtube.com/watch?v=aISsu5k85mQ

http://www.engadget.com/2012/05/22/the-engineer-guy-shows-how-a-smartphone-accelerometer-works/

Another possibility would be to use a piezo element in some sort of padded pouch so it doesn't get punched to death ]:D Have one in the target area, and sample the signal from it with an op-amp circuit and the ADC of an arduino or whatever mcu board you happen to be using.

Then, have something in your program that will map that data to one of several discrete options, from featherweight to Hulk Smash, and output THAT data over your serial port to the computer. That's how I'd approach the problem anyway, it may not necessarily be the best but it makes sense in my head.