So, I acquired a USB OTG cable from ebay for under $1 (great option as long as you don't mind ordering directly from China and waiting weeks for it to arrive... and I'm a cheapo who hasn't upgraded his WinXP netbook, so that works for me!).
I hooked up a USB mouse, in an attempt to make my teeny tiny Quake device ( http://www.fvfonline.com/forum/viewtopic.php?f=4&t=3810
) as much like a teeny tiny PC as possible.
Well, mouse control obviously hasn't been considered in QuakeDroid, but it does function at a system level in Android (just like OGG decoding! XD ), and shows a mouse cursor on the screen.
It thinks my screen on QuakeDroid is rotated 90 degrees to the left though (same with the softkeys being along the right side of the screen), so when I move the mouse up, it moves left on the screen, moving the mouse right moves the cursor up, etc.
It acts as a "touch" rather than functioning as actual mouse1 or other mouse motions. If I hold down mouse1, then I can "drag" the screen around just like with touch aiming. Double-clicking makes it fire, and I can click through the menus (sideways...).
And if I use the mouse cursor to press any of the onscreen controls, it activates that control, just like a touch.
So actual mouse controls might be viable, assuming the mouse can be separated from touch controls. But I'm not sure how possible that is....