PokéMate is a mobile phone application developed by Square-Enix. Essentially it is a system to allow for messages to be sent from person to person such as e-mails

Chatroom

There is a chatroom function where your Pokémon, and other people's Pokémon come in and allow you to chat
When the messages are sent, they are marked with your name and the signiture Pokémon of yours.

Pokémon

When you access the game for the first time, you receive one random Pokémon, you also get 10 PokéBalls to allow you to catch Pokémon
Simply enough, you find a Wild Pokémon and you catch it, however originally there are only 3 Pokémon you can catch, all random
However with the subscription to the service each month, more Pokémon become available and you get 5 more Pokéballs to capture the Pokémon with. You can also buy new Pokéballs for a small price seperately

Storage/Partners

All your Pokémon are stored within Boxes in the system just like the Pokémon in the general GBA games. You can select the Pokémon here to use them as your mascot Pokémon
This also allows you to see a Pokédex entry for the Pokémon which also includes information on when you caught it

Currently PokéMate is only out within Japan but it was shown at E3 and is likely to have a US release at some point in 2006