The
Travel Kit SP comes equipped with three individual items: an adapter piece which plugs into the GBA SP power adapter port, a set of stereo headphones, and a DC car adapter. The DC adapter and stereo headphones both plug into the adapter piece. In fact, the adapter piece can accept any device that would normally plug into the power adapter port, and can also accept any standard sized headphone. If you are a gamer on the go that likes to listen to the powerful audio of the GameBoy Advance, but cannot let others hear, then this adapter solution is your answer. You can now use any GameBoy devices, along with a headphone set at the same time you're charging it.
When using the car adapter, the GBA SP does not have to be off, although in order to charge fully, it would probably be wise to do so. Nevertheless, using a car adapter while on small or large trips can help to ensure your GBA SP does not die while in the middle of an important session of Metroid Fusion.