I got a bundle of GBA SP accessories because I wanted another headphone adapter, but it came with an FM radio cartridge that seemed interesting until I got it and it turned out that it just uses the GBA for power, so it just displays the boot screen forever.
But it is kind of cool in the context of playing tunes while playing something on a DS, where it does still get power and still work. Not that I would realistically do that, though?
