I hope this doesn't degenerate into a screaming "stair head rammy" (Scottish expression) over stall speeds. Let's just agree that we all are aware of AoA.
SSD, I too would trade a few instruments for such a device, ASI being one of them. Although it may be of some use for Nav in the event of GPS failure.
The wooly stick ahead of the wing? Ok but a little crude. For GA light stuff I don't think sensors on flaps or other configuration changing devices is necessary.
It needs to be neat, tidy, and do a reasonable job on a clean a/c. If it were to read "stall" when clean and the flaps are down it is erring on the safe side.
If such a device could be built at a sensible price I think it would be taken up, especially if it could be retrofitted to anything. An expensive box of electronic junk costing an arm and leg to be certificated will not be.
My daft idea of lashing a fuel gauge tank sender unit wind vane thing to an u/c leg reading to a fuel gauge with instant read out is still on the drawing board, my a/c being permit powered I may try something this summer just for fun if nothing else. Any advice gratefully received.