Another idea for Shepherd: make your NIT into a WiFi USB host for your N900 (posted here by request):

(Prerequisites: an ad-hoc wifi network set up between the N8x0 and the N900, and a USB OTG adapter for the N8x0)

When you plug a USB device into your N8x0, Shepherd will notice and can ask if you want to start the ad-hoc wifi network. Then, on the N900, when you connect to the ad-hoc network, Shepherd can ask if you want to mount the USB devices from the tablet on your N900 (via sshfs probably), and open the file manager for you.