I've had bats in my attic, or at least in the gable vents of my attic. I needed to inspect the situation, but I REALLY REALLY didn't want to physically go walking around the attic to inspect for bats. So, I built Atticbot, which technically is just an RC vehicle that I hoped would be able to traverse the rafters. I used $5 worth of yardsticks to construct some wheel-like things, mounted them to some cheap continuous-rotation servos, connected the servos to an RC receiver, and that was pretty much it for the mechanics.
For video I mounted a cheap gimbal/camera so that I could look around left/right/up/down, connected that to a cheap 5.8ghz transmitter. It worked, but not as well as I hoped. I think I need more battery juice to the servos. They tended to not want to turn. Nevertheless, it did drive across the attic, inspect the place the bats used to live, and found the place that they've moved to. I wound up having to retrieve it though, it was too low on juice to get back.
Sorry about the lack of audio on the video, my setup doesn't have a microphone.
The cost of the thing was around $25 for the yardsticks and servos, radio control could be done for as little as $40, but I've probably got $150 in my radio and receiver. Video could be had for around $100, but I've probably got around $150 in the monitor/transmitter/camera in this video. So, total, you could probably build it for around $200, and after you're done you'd have plenty of generic RC and video parts for another RC/Robot project.
Navigates around the attic via RC controller, transmitting video back to the controller.
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/atticbot