I’ve made a module that uses the Mac DiskArbitration framework, allowing us to monitor when disks and volumes come and go, as well as to suppress mounting of volumes when a disk gets inserted (useful for disk tools like my iBored).
Here’s the code with a sample project: http://files.tempel.org/RB/DiskArbitration%20Suppress%20Mount.rbp.zip
Use it as you like I give it to the public domain, as it’s just sample code, nothing original (claiming a copyright on sample code is kind of silly, anyway, IMO),