PIN entry: Add support for hardware keyboard (Bluetooth)

I have a nifty bluetooth numeric keypad which I've attached to my tablet. The idea is to use it as an external keypad to open a lock (have an August lock without keypad), with the tablet sitting inside.However it appears that even though the keypad pairs nicely and works on other web pages and apps, the AT pin-screen does not process keypad input. I've tried on a PC as well. One has to use the mouse to click on the onscreen pin keypad.

Request: Please consider supporting PIN keyboard entry, 

NB: This should not show the touch effect (the quick shade-over grey shadow, which briefly passes over the pin buttons when pressed on-screen), because that would reveal the PIN to any observer, of course.