Obvious answer: as spare part for other wiimote accessories (or make your own extension cord)
Apart from that there isn't much to do - wiimote accessories use the SPI protocol and you could make your own bluetooth thermometer or whatever, but for the same reasons console homebrew is a dead art (ie we have affordable androids, affordable arduinos, and affordable raspberrys) there's no practical advantage in pursuing this more-complicated-than-it-needs-to-be hackjob solution