These are devices that are needed for developers. Currently, some developers have no devices at all, and some have only one device or another. This makes it difficult to get issues and bugs addressed in timely fashions -- not to mention getting features added at all! (In fact, we have people actively working on device support, but without devices!)
You may notice that there are fewer devices here than in Amarok 1. At the moment, these are the only planned device types. That doesn't mean that other device types will never make it in, but the entire device plugin framework is being restructured, and these are considered the highest priority types.
If you can help us out, please email amarok-device-donation AT emailgoeshere DOT com to get the ball rolling. Thanks!