The Poké Transporter GB is a tool for the Game Boy Advance that allows you to transfer Pokémon from the 1st generation (Pokémon Green, Red, Blue, and Yellow) or the 2nd generation (Pokémon Gold, Silver, and Crystal) to the 3rd generation games (Pokémon Ruby, Sapphire, FireRed, LeafGreen, and Emerald).
It works on both emulators and consoles.