Here's a neat little product we came across that plugs into the back of a Gameboy Advance. Among other things, it lets you look at signal waveforms, like you would with an oscilloscope.

You can set it up to display as many as four channels of data, such as O2 voltage, MAP or TPS sensor, or even ignition trigger signals. It's not a data logger, but you can see stuff happening in real time.

It gets its power from the Gameboy's 3.3v battery, which means that for signals greater than 3.3v, you need to use a voltage divider (big deal, two resistors) to cut the signal down to size.

The company is educatingmario, and the product is called the Captigate. I ordered the package shown below, for just $67, including shipping from Switzerland. My order included an extra set of cables to chop up and experiment with.

You can get the new Gameboy Advance-SP from Target for $99.

Captigate with cables

Captigate close ups

Channel 1 connected to signal generator (forgot to put my finger over the RedEye thingy)

Same waveform on scope. Period is 20 msec.

Four channel display shows coil drive signals from our Direct Ignition test generator: