From Bulbapedia, the community-driven Pokémon encyclopedia.
The Xtransceiver (Japanese: ライブキャスター Live Caster) is a key item in Generation V. The Xtransceiver can be used to communicate with other players nearby using the C-Gear's wireless feature, where up to 4 players can talk to each other using a radio-like system, and if they have a Nintendo DSi or a Nintendo DSi XL and camera function is not disabled, see each other. The Xtransceiver can also be used over the internet by selecting it at the Global Terminal in Pokémon Centers.
In the anime
Shooti was the first person seen with an Xtransceiver in the anime. It first appeared in BW010 where Ash contacted Shooti on a built in Xtransceiver in Current Town's Battle Club computer. It contacted Shooti and Ash asked him for a battle. In BW013, Bianca was also shown to have one where she contacted Professor Juniper.
In the manga
In the Pokémon Adventures manga
The Xtransceiver first makes it appearance in an advertising commercial for the device. The commercial shooting is interrupted by a wild Denchura but Black saves the day by defeating it. Later, he and White are each given Xtransceivers as thanks.