Since Trip is no longer a mod, and some of the info in the old FAQ was outdated, I’ve written a new FAQ and am starting this thread over again. Please ask any and all questions related to the wireless adapters and the Mystery Gift function here, and PLEASE read the entire FAQ before asking a question. Thanks.
1. Q: What is the wireless adapter?
A: When FR/LG first came out, each game came with a wireless adapter. They can be used for everything the link cable can be used for, plus a few new things. However, FR/LG games no longer come with them, but you can buy them for $10 each. The supposed range is 30 feet, but it has been sometimes known to work at farther distances.
2. Q: What games does the wireless adapters work with?
A: FireRed, LeafGreen, and Emerald, If counting only Pokémon games.
Other games need to have the wireless Adaptor support programmed in, as a result not many games supported it. The wireless adaptor also supported a Single cart powering several GBA. Many of these are GBA NESClassic games.
3. Q: What new things can you do only with the wireless adapters?
A: When using the wireless adapters, you can now go into the Union Room, where you can battle and trade with other people playing the game that are in range. You can also use the Berry Crush and Mini-game features. More info from the main site:
4. Q: What is Mystery Gift?
A: Mystery Gift is a function in FR/LG/E that allows your game to communicate with Wonderspots. These are machines, available at Nintendo-sponsored events like Pokemon Rocks America, which send data to your game. They so far have been used in the US to give out the Aurora and Mystic Tickets.
5. Q: How do I get Mystery Gift?
A: Go to any PokeMart and look at the counter. There should be a paper there. Go up to it and press “A,” then complete the survey with the words LINK TOGETHER WITH ALL.
6: Q: How do I use Mystery Gift with other games?
A: Unfortunately, you can’t. Mystery Gift can ONLY be used with Wonderspots, not other games, and the Aurora Ticket and others aren’t transferable in any way.
7. Q: Since the DS has wireless features, can you use it to trade with a GBA with a wireless adapter?
A: No. The DS has a completely different wireless system than the GBA's wireless adapter. You can't trade between a DS and a GBA OR a DS and another DS using the GBA Pokemon games. (There is a way to send Pokémon GBA to a DS game using Pal Park. However, this covered in the 4th Generation section, and We're talking about keeping it in the GBA games.)
If any more questions are asked often enough, I'll add them here. That ended up being much shorter than I had expected.
Edit: 23/12/2011 -Big Nutter
Apparently there was a GameBoy Micro version of the Wireless adaptor, but I never found one. (The Gameboy Micro was a GBA as small as Nintendo could make one. Almost all Accessories for the GBA or GBA-SP were incompatible.) The Wireless Adapter does fit the GameBoy Player add-on for the GameCube, the only software that could use it was the Gameboy Advance games that could use it in any other GBA/GBA-SP.