wot dashed said, there is a lapse (usually about 0.3 to 0.5 s) before the video starts / photo and the frame rate is not good for fast moving. We have a cheap chinese (campark, same as apemap) version that works well for the price for larger and slower stuff (fox, hedgehog, badger) but is only reasonable for birds in daylight so wouldn’t capture bats even at dusk, they’re way too quick. I suspect getting something that could video but isn’t disturbing (i.e. no flashlights, good infrared and high enough frame rate to capture their flight) would be crazy expensive.
If you can solder, you can ‘make your own’ heterodyne listening device cheaply (e.g. bat detector). Unfortunately the cheap versions like that can’t tell you the frequency you are listening to so it’s a guess what species you have, though usually pipestrelle.