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I need a miniature transmitter + receiver + speaker.  I would like to keep this all as miniaturized as possible and run on batteries as long as possible.

The idea is that when the transmitter button is pushed the receiver is initiated to cause some sound such as a chirp or some programmed sound to play on the miniaturized speaker.

Any ideas?
Sure. I can build you a system that's about the size of a small coin cell and the battery will last around a year. Will that work? Cost will be around $25,000 for the first unit. Can go smaller than that (you did say as small as possible), but cost increases rapidly.

Or, you could, you know, use numbers. Numbers like how small, how much range and how long the battery should last.
Consider building your own very tiny transmitter, following the attached Scientific American article from 1968. Any AM radio will pick up the signal.
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All, thanks for the ideas.

Lyndon, a button cell size transmitter and a button cell size receiver with mini speaker would be great. They need to be addressable so the units don't interfere with each other and the batteries should last about a year if the transmitter button is pushed briefly two or three times / day.

How many units of each would we need to produce to get the cost down to $5 for the pair?
My SWAG at a minimum quantity for that pricing would be around 30,000/year. But that's probably a bit low. I was kidding about doing this design: I don't do consumer products and try to avoid wireless.

$25k is in the ballpark of a basic hardware/firmware design of a similar device I know of. You'd have to add certification costs and of course, mechanical design for the enclosures.

Now, if the size could be a bit larger than that, then it becomes feasible at a much lower cost. The common 433MHz transmitter/receiver modules like jremington linked to are easy to use and you could probably fit something about the area of around two postage stamps.
Thanks lyndon!

If you one of anyone that might be interested in taking on the design please let me know.

By the way, if you don't mind me asking, what's the other hardware/firmware product you know of that cost about $25k to design?