Star Wars Rogue Squadron III: Rebel Strike (2003) has an unnecessary connectivity feature with a Gameboy Advance.
Exclusively available in the 2-Player Vs mode, a GBA can be linked to display the wingman commands. In other words, if the player didn’t want to tap orders via the Gamecube controller’s d-pad, you can awkwardly take your hands off the controller, tap the d-pad on the GBA instead, then pick up the Gamecube controller again. Intuitive, right? Also, 2 GBAs can be links too, one for each player, if you really want to get nuts.