Firstly, to clear up a misunderstanding about modern drives - all modern hard drives (ATA, SATA, SCSI etc) have a list of bad blocks stored in their firmware. No, you can't access this list. Every drive made has bad sectors. Every drive made has spare capacity so it can automatically remap bad sectors.
What happens is when a drive sees a bad sector, it tries to silently remap that sector to somewhere nearby, in an area reserved for this purpose. This happens without you being told anything. I personally think that the SMART status should indicate that this is happening...
Once you are seeing bad sectors at the higher level, that means that the drive has run out of spare sectors to remap these bad sectors and you're really in trouble. The drive will go pear-shaped in the near future. No, really, it will.
Having said all that, there is a service mode for iPods, which is described on this page. When in diagnostic mode, you can do a hard drive scan, to scan for bad blocks. You can also go one step further and do a full read/write test -- this also has the side-effect of remapping what bad sectors it can, but it will erase the data on your iPod. You have been warned.

