Yes, WIRELESSES is a Scrabble word!

Letter values in Scrabble US: W 4, I 1, R 1, E 1, L 1, E 1, S 1, S 1, E 1, S 1.

Is it a valid word?

WIRELESSES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

medium for communication
transmission by radio waves
an electronic receiver that detects and demodulates and amplifies transmitted signals
a communication system based on broadcasting electromagnetic waves

Also: radiocommunication, radio receiver, receiving set, radio set.