Here's a link to a study from the U of Arizona on the effectiveness of ultrasonic devices (does not address LEDs) on pests. Their comment regarding rats is:
In a study testing the effectiveness of an ultrasonic device
on rats and mice, it was found that they had a mild aversion
to the sound (Greaves and Rowe 1969). However, this dislike
diminished over time, especially after a reliable food source
was discovered near the sonic device. Even after the food
source was removed the rats and mice continued to explore
the room with ultrasonic sound, expressing habituation to the
sound. Habituation is a decrease in response to a stimulus,
and is often cited in studies testing the efficacy of sonic pest
devices. For example, initial sound emitted from sonic devices
may be interpreted as a threat, but after a short period passes
without physical harm pests grow more comfortable. The
researchers in this particular study do suggest that well placed
ultrasonic devices may aid in repelling pests.
https://extension.arizona.edu/sites/...Z1639-2015.pdf
My takeaway from this is that one's results can be good if you're repelling roaming rodents so they never gain a foothold in your rig, but once a stubborn one gets in and finds food, all bets are off. The units might be more effective in an RV due to it's small size. In a building, they could inhabit a relatively quiet space and gradually move into the louder, more protected area, acclimating to the sound as they go.
For $30 it's worth a try, $100 or more, I don't think so unless I really had a problem and tried everything else.
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