Not for your iPod / iPhone / (not iPad, until it gets a camera), but for your Mac:
, which uses the iSight camera to scan bar codes on books, magazines, etc. Here's a comic book plug-in
for it. YMMV - I haven't tried it.
Whoa: Just looked at "IntelliScanner" noted above. That's pretty comprehensive... but $99 USD
compared to $18 USD
Probably a case of "you get what you pay for"