Answer: 11, for one retiree in Taiwan.
Chen San-yuan first went viral in August when he was spotted playing the game with 11 devices mounted to his bicycle. He has since gotten a waist mount, arguably a safer move since he can now go around looking at 11 screens while on foot rather than a bike.
Chen’s hobby costs him about $1,290 a month for phones, lures to pokéstops and other in-app purchases. The external batteries and charging cables that he carries with him give each of his devices about 20 hours of battery life while he’s out and about. The retiree was introduced to the game by his grandson, and his unique method for playing has turned the street where he lives into a tourist stop. According to The Verge, he told a local news outlet that he mostly avoids gym battles because he thinks it would be unfair to other players. Instead, he prefers to spend his time catching and upgrading rare pokémon.