--Connected audio connectors for speakers and mic.  J7 is speaker and J6 is mic, according to Summit board schematic found at https://pubs.gumstix.com/boards/SUMMIT/PCB30001-R2734/PCB30001.pdf.  Also connected USB power for speakers to 5V DC-DC converter.  Tested speakers using phone as audio source--sound quality is fair, but volume is good.
--Started work on getting IMU up and running.  Found a good tutorial at https://github.com/ptrbrtz/razor-9dof-ahrs/wiki/Tutorial and started working through it to test the IMU.  Currently reading data from the IMU in the form of Euler angles.  Not sure if Euler angles are what we want, or if we want things like compass heading, etc...  Need to run through the calibration procedure and figure out a way to adjust to the coordinate system set up in the software, since it is different from the axes printed on the board
--Discovered that on the Gumstix, the IMU is at /dev/ttyUSB1 and the GPS is at /dev/ttyUSB0. **NOT SURE IF THIS IS CONSTANT**
--Modified the mounting of the IMU.  Changed the USB breakout board from being mounted perpendicular to the IMU with a straight header to being mounted parallel and attached to the bottom of the IMU using a right-angle header and double-sided tape.  I thought the perpendicular mounting might be too vulnerable to breakage and I didn't like the cable routing in that setup.  The parallel mounting is much more compact and secure, and keeps the USB cable out of the way.