I just found this yesterday, and I'm not sure if anyone else has seen it:
https://www.youtube.com/watch?v=Sj2ncmVmaB0
These are small siren units produced by Audio Lighting Alert Inc. that are used to warn beach-goers of hazardous waters. The siren they use is a Whelen WPS-2901, and it appears that they use a 2801 in other versions. I just thought this was kind of interesting.