They are close, but no cigar! You might be able to force a Sansa plug into an iPod, or maybe the other way 'round but one of those plugs is just slightly larger than the other. I think the Sansa is an off the shelf standard part, and the iPod is a custom to Apple.
Apple recently told all third party iPod accessory makers they could no longer use the Apple female connector in their products (same connector as on the ipod itself) but could continue to make plugs that go into the iPod (ie: docking connectors). The company I work for makes an amplifier that hooks up to the ipod and shows the metadata on it's own control panel. It connected to the ipod via a cable with male ipod ends on both ends of the cable. Now we have to put a DIFFERENT socket on the amp, and it looks like we are going to use the same one as on the Sansa. (which means we have to label the cable with IPOD and AMP in big letters on the cable so the user doesn't mess up).