Passive intercom system?

[slackerinabox]

I've been going to church lately - before you jump down my throat, I'm not all that religious but think it's good for the kids.. When our youngest acts up one of us retreats to the basement nursery that's set up for these situations, but there's no speaker relaying the sermon in the room. My wife often has to spend 20 minutes down there with the kiddo and misses the reason she came to church in the first place (she's more into it than I am, but she's also best at calming the toddler down). Any relatively affordable system I could recommend or donate? Hopefully wireless and strong enough to transmit from the ground level to the basement.

It's a small neighborhood church, I've been to megachurches with really elaborate systems, but let's cap this at under $500. They use a mic and speaker system, but it's really old school and I don't see any mixer/amp setup (I think it's from the 60s)

 

[Kaido]

Might be able to get by with a cheap Bluetooth setup. Not sure how well it would work through walls. Anker sells a combo TX/RX box for $30 each: (you'd need 2)

https://www.amazon.com/Anker-Bluetooth-Transmitter-Receiver-Headphones/dp/B00E174RTS/

However, the cheapest cable is better than the most expensive wireless system; I'd spring for a drill & go donate some time & effort to running wire into the remote location. If it's a basic mic/speaker setup, it should be easy enough to run a second set of lines to the basement, add a small amp that lives inside a wall-mounted volume control, some speakers, and some wiremold to hide everything. These speakers come with wall-mount brackets for $30 shipped:

https://www.amazon.com/Acoustic-Audio-AA321W-Surround-Speakers/dp/B00KSLX706/

This is a wall-mounted amp with a volume control for $30:

http://www.parts-express.com/pyle-pvc1-wall-mount-rotary-stereo-volume-control--310-2612

Or just a mini-amp for $30:

https://www.amazon.com/Lepy-LP-2024A-Amplifier-Stereo-Supply/dp/B00ULRFQ1A/

Basically, run the audio lines (source or speaker cables, whatever is available for output) into the room (drill holes etc.), put the amp somewhere out of the reach of children (or use the wall-mounted box so all the wiring is hidden), mount the speakers on the wall, and hide everything with some Wiremold from Home Depot. Either amp would let you control the volume in the room independently of the main room.