I love this idea. I've just started getting into birds, and I wish I had steady enough hands to build a solar+battery version of this I could stash in the woods for a week.
Is there anything like birdnetpi, but with an ultrasound transducer for bats? I know I have them zooming around, but rarely see them, and would love to know more what their activity is like here.
Oh, checking out the AudioMoth linked elsewhere, looks like that works for recording birds and bats. Down the rabbit hole I go.
Along the lines of piaware, also checkout https://liveatc.net. If you live near an airport that's not currently served by the site you can set one up moderately easy.