Sound activated lamp that actually works quite well.

Those of you who have been around as long as I have will shudder at the mere mention of "clap switches" where you had to physically clap your hands or shout to make things turn on and off. Really terrible things. But here we have a common style of Chinese LED lamp with an extra module that not only combines a light sensor, but also a sensitive audio circuit that detects a natural speaking level voice and turns the lamp on for about 45 seconds. So you could either use it to add a switchable lamp in an awkward location, or as a sound activated intruder deterrent.
As things like this go it's actually quite well implemented.
Bizarrely it even uses a very retro CD4011B CMOS logic chip to implement the sensing and timing.