Depending on how current your Debian installation is you might have DBUS & HAL installed. There's a command-line tool for DBUS which you can instruct to listen for added devices: (example is a flash drive)
Code:
> dbus-monitor --system --profile 'interface=org.freedesktop.Hal.Manager, member=DeviceAdded'
sig 1246865406 537113 2 /org/freedesktop/DBus org.freedesktop.DBus NameAcquired
sig 1246865413 849690 6387 /org/freedesktop/Hal/Manager org.freedesktop.Hal.Manager DeviceAdded
sig 1246865413 898142 6390 /org/freedesktop/Hal/Manager org.freedesktop.Hal.Manager DeviceAdded
sig 1246865414 883198 6393 /org/freedesktop/Hal/Manager org.freedesktop.Hal.Manager DeviceAdded
sig 1246865414 883255 6394 /org/freedesktop/Hal/Manager org.freedesktop.Hal.Manager DeviceAdded
sig 1246865414 903331 6403 /org/freedesktop/Hal/Manager org.freedesktop.Hal.Manager DeviceAdded
sig 1246865415 53744 6430 /org/freedesktop/Hal/Manager org.freedesktop.Hal.Manager DeviceAdded
sig 1246865415 97264 6449 /org/freedesktop/Hal/Manager org.freedesktop.Hal.Manager DeviceAdded
