every 6DOF imu will serve you great, just add a SD card for collecting data and here you go. As always, post-processing data is the best idea if you don't have SD space problem, or some reaction to do in real time in response of some input.
Cheap IMU: SparkFun 6 Degrees of Freedom IMU Digital Combo Board - ITG3200/ADXL345 - SEN-10121 - SparkFun Electronics? (maybe not the cheapest, but this is the "entry point" price)