OP here, didn't have an account so I made one to comment! The devices that were installed are like one-way doors, so the bats can leave but not get back in. This meant the ones still in the walls got distressed when the ones outside didn't return. They're classed as "wildlife" meaning they can't be exterminated, so this is one of the easiest, non-lethal solutions to getting them out. It's been about a week, and the wall-scuttling has calmed down as they filter out, but it was like living in a haunted house the first few nights. Plus, over the course of the week 7 bats got to the interior of the house through vents (yeesh.) We caught those safely and returned them outside, but waking up in the middle of the night to a bat in your bedroom is not an alarm I'd recommend.