An interesting piece of hardware that overlapped both the games and the TCG was the GBA E-Reader. Two versions were released in Japan: the original e-Reader (without a link cable port), which could read cards to unlock game content, etc.; and later the e-Reader+ (simply “e-Reader” in Australia and North America), which came with a link cable port to connect with GameCube games such as Animal Crossing and with other Game Boy Advance systems for games such as Pokémon Ruby and Sapphire. The e-Reader was only considered successful in Japan.
Original E-reader in Japan that didn’t have link port support to connect it with other games.
There were various Pokemon mini games and applications that could be loaded into the e-reader from the Expedition, Skyridge and Aquaolpolis sets.
This video has a great review of all of the mini games and which cards you needed to play them.
This site also has a comprehensive list of the cards released and downloads for the save files.
They also have some interesting images like this image below of the retail point of sale for the E-Reader back in the day.
