Well there are modules which combine I2C accel's and gyro's on eBay that are cheap and seem fine (I've an LSM330 one like this: http://www.ebay.co.uk/itm/6DOF-IMU-LSM330DL-LSM330-sensor-board-for-RC-robots-FPV-projects-/260946248174?pt=Radio_Control_Vehicles&hash=item3cc19bc1ee). They may be 3.3V or 5.0V but not a big problem with I2C if you don't mix voltages on the I2C bus.
There are also 9DOF modules (accel/gyro/magnetometer) which might be worth considering (GPS can only give direction once moving).
GPS receivers - probably any modern module will be OK for outdoor use - look for cheap and the voltage you'd prefer (and whether you want separate antenna or integral).