I’m trying to create a proximity/motion sensor to trigger a soundclip from a small MP3 player (cheap little knock-off from eBay). The MP3 player would be constantly playing the soundclip in an infinite loop. I’d attach a speaker to the headphone jack of the MP3 player, then interrupt the cable (somehow?) with a simple on/off toggle to interrupt/transfer the sound to the speaker. The toggle would be controlled by a proximity/motion sensor. I plan to have about 6 of these running at the same time being triggered by visitors to the exhibition.

Does this sound plausible / achievable? What components should I look out for at Maplins? Where should I look online to find help? Do you think this type of toggle/sensor combination exists off the shelf? What would it be called? Can an outside ‘security’ light be frankensteined to work? Any help / pointers would be massively appreciated! What am I missing?