My optical drive bay was misbehaving so it needed replacing with something. I had no need for the commercial hard drive bays you can buy. Instead, I decided to put a Raspberry Pi in there for projects on the go. By connecting to it using VNC by setting up a hotspot on my laptop I can access the Pi desktop headless. See more details in the Instructable
Raspberry Pi Zero W although Raspberry pi b might fit if you desoldered the headers.