libsicksaxis is a C library that lets you connect a Sixaxis or a DualShock3 to the Wii and read its data. It also lets you turn on and off the controller LEDs, enable or disable the rumble and get and set the controllers' bluetooth MAC address.
You will need the DevkitPPC to compile it.
This fork is an attempt to support more PS3 devices by including their Vendor and Device IDs in the library.