Unreliable, slow, fun.
The best part was holding it up to the dogs bark, then watching her hunting for the "other dog" after the echo. It isnt practical for speaking but it was great fun.
The app worked right away with one Mac, but not with another on the same OS. At any rate, the delay was too substantial to use for live speaking. However it has proven useful as a building-wide "paging system."
Fix the lag and connectivity and this will be a solid value instead of a novelty.
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AirMic - WiFi Microphone