Sometime over the holidays, David Morgenstern accidentally activated a series of technician-level diagnostics on his iPod, including the following:

Keytest: Checks the function of the click wheel. It prompts you to click each button and turns their names from gray to black if they pass.

FlashScan: Does a longer scan of the flash memory.

PowerTest: Looks at the battery and other power hardware.

WheelTest: Checks the scrolling capability of the clickwheel.

TouchWheelID: Checks the ID of the clickwheel — no idea that it needed to be carded.

Playback: Checks the headphone out port and makes a loud, annoying tone.

Kind of cool and his recent post over at The Apple Core explains how to access the diagnostics and what each is used for.

Give it a gander and if you've found some useful tricks for your iPod, let us know over in the comments or forums.