usb dataloggers
 

easy cheezy, looks like a keyboard to your computer and sends "keystrokes" to the open application:
DIY
V-USB - A Firmware-Only USB Driver for Atmel AVR Microcontrollers
2 input ($10)
SparkFun Electronics - AVR Stick

Put a scoche of circuitry on it to monitor injector dwell and vss frequency and read it from System.in?

or reflash it to use the mpguino diode interface (with an isp programmer, and be able to account for injector opening time)?

or log/display whatever analog signals you want to monitor on your laptop (MAP/TPS?)

Battery pack probes? Current?