What you are probably looking for is an accelerometer. That is how vibration is typically measured (at least that is how I do it on my microscopes). You can easily build a simple datalogger and connect it to your accelerometer. Depending on what you want to measure, you might need one for translation in each axis and one for angular rotation about each axis (a total of 6).
You also might wanna try using a piezzo disc (im not sure how to write it), it made out of a special crystal - its produces small voltage when vibrates so you can process the voltage using A to D and a uC and know how much vibration your rocket has...