You've inspired me! I've got 4 x 5.25" bays unused on my case and I'm thinking I could do something like this with a cheapo android tablet I never use.
Could you include a shot of the inside?
Im not 100% sure but I think you can take the battery out and it will still operate as long as the pc is powered on.
Did you cut the male usb end from the power cord and splice in a motherboard compatible header (so you can plug directly to the motherboard usb headers) or do you have internal usb port on your board? Its a little different from what I originally thought but still quite nice
You got me researching different software and I'm wondering if you came across Roccat Power Grid? It's a free, simple, and extendable platform for using a table/phone as a monitoring screen. There are several functions like pressing on a drive opens it on your PC and even individual app volume control. Oddly enough, no app seems to do this over USB (yet), all require a pc server and the device to connect over wifi.
The mount will have to be custom (and probably starting my own project log). Not a single tablet mount for a pc's drive bay area exists, everything is for cars/walls/swivel arms.
Damn you and this neat thing you've done!